U.S. patent number 10,285,678 [Application Number 15/382,731] was granted by the patent office on 2019-05-14 for micrograft for the treatment of intracranial aneurysms and method for use.
This patent grant is currently assigned to Neurogami Medical, Inc.. The grantee listed for this patent is Neurogami Medical, Inc.. Invention is credited to Bartosz Bojanowski, Stephen J. Hebert.
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United States Patent |
10,285,678 |
Hebert , et al. |
May 14, 2019 |
Micrograft for the treatment of intracranial aneurysms and method
for use
Abstract
A device for occluding a vasculature of a patient including a
micrograft having an absorbent polymeric structure with a lumen of
transporting blood. The micrograft has a series of peaks and
valleys formed by crimping. The occluding device is sufficiently
small and flexible to be tracked on a guidewire and/or pushed
through a microcatheter to a site within the vasculature of the
patient. Delivery systems for delivering the micrografts are also
disclosed.
Inventors: |
Hebert; Stephen J. (San
Francisco, CA), Bojanowski; Bartosz (San Francisco, CA) |
Applicant: |
Name |
City |
State |
Country |
Type |
Neurogami Medical, Inc. |
Mountain View |
CA |
US |
|
|
Assignee: |
Neurogami Medical, Inc.
(Mountain View, CA)
|
Family
ID: |
55272698 |
Appl.
No.: |
15/382,731 |
Filed: |
December 18, 2016 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20170143319 A1 |
May 25, 2017 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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14997008 |
Jan 15, 2016 |
9999413 |
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62105648 |
Jan 20, 2015 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61B
17/0057 (20130101); A61B 17/12172 (20130101); A61F
2/06 (20130101); A61B 17/12031 (20130101); A61B
17/12154 (20130101); B29D 23/18 (20130101); A61B
17/12145 (20130101); A61B 17/12177 (20130101); A61B
17/12113 (20130101); A61B 17/12118 (20130101); A61F
2/07 (20130101); A61B 17/1214 (20130101); B29D
23/00 (20130101); A61B 17/1215 (20130101); A61B
2017/0053 (20130101); A61B 2017/00526 (20130101); A61B
2017/00898 (20130101); A61B 2090/3966 (20160201); A61F
2/95 (20130101); B29K 2105/0035 (20130101); B29K
2067/003 (20130101); A61B 2017/00867 (20130101); A61B
2090/0807 (20160201); A61B 2017/1205 (20130101); A61B
2017/00778 (20130101); A61B 2017/12054 (20130101); A61F
2002/077 (20130101); A61B 2017/00893 (20130101); B29K
2105/25 (20130101); A61B 2017/00942 (20130101) |
Current International
Class: |
A61F
2/06 (20130101); B29D 23/18 (20060101); B29D
23/00 (20060101); A61B 17/00 (20060101); A61B
17/12 (20060101); A61F 2/07 (20130101); A61F
2/95 (20130101); A61B 90/00 (20160101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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203885554 |
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Oct 2014 |
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CN |
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WO 94/09705 |
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May 1994 |
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WO |
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WO 03/037191 |
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May 2003 |
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WO |
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WO 2004/069059 |
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Aug 2004 |
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WO |
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WO 2006/034149 |
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Mar 2006 |
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WO |
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WO 2006/088531 |
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Aug 2006 |
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WO |
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WO 2012/135859 |
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Oct 2012 |
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WO |
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WO 2013/119332 |
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Aug 2013 |
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WO |
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WO 2016/044188 |
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Mar 2016 |
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WO |
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Other References
International Search Report and Written Opinion dated May 3, 2016
for International Application No. PCT/US2016/013638. cited by
applicant.
|
Primary Examiner: Stransky; Katrina M
Attorney, Agent or Firm: Gershon; Neil D.
Parent Case Text
BACKGROUND
This application is a continuation of application Ser. No.
14/997,008, filed Jan. 15, 2016, which claims priority from
provisional application 62/105,648, filed Jan. 20, 2015 . The
entire contents of each of these applications are incorporated
herein by reference.
Claims
What is claimed is:
1. A vascular implant configured for placement in an intracranial
aneurysm of a patient to aid thrombus formation in the aneurysm,
the vascular implant comprising: an inner helical coil composed of
a metallic material and having a lumen formed therein extending
from a proximal portion to a distal portion, the metallic material
being radiopaque, the lumen being sized to induce blood flow
through the lumen in a capillary effect; and a non self-expanding
polymeric braid extending over and attached to the helical coil,
the braid having a distal opening, the braid extending to cover the
proximal portion and the distal portion of the helical coil, the
braid formed by a plurality of yarns, and the yarns formed by a
series of polymeric filaments, the vascular implant configured for
aiding thrombus formation in the intracranial aneurysm, the
vascular implant receiving blood flow therein through the lumen to
fill the lumen as it moves from a delivery catheter to placement
within the aneurysm, the vascular implant further receiving blood
through spaces between the yarns and spaces between the
filaments.
2. The vascular implant of claim 1, wherein the yarns form a
permeable structure such that blood is transported between the
yarns and through the device.
3. The vascular implant of claim 1, wherein the implant is heat set
to form a coil shape.
4. The vascular implant of claim 1, wherein the braid has a range
of between 80 and about 600 picks per inch.
5. The vascular implant of claim 1, wherein the braid is composed
of PET.
6. The vascular implant of claim 1, wherein the vascular implant
has an outer diameter less than about 0.027 inches.
7. The vascular implant of claim 1, wherein the braid forms a fluid
barrier which maintains a degree of permeability.
8. The vascular implant of claim 1, wherein the braid has a wavy
form having a series of undulations.
9. The vascular implant of claim 1, wherein the braid has an uneven
braid surface.
10. The vascular implant of claim 9, wherein individual yarns of
the braid bulge outwardly to create the uneven braid surface to
create localize hemodynamic turbulence and flow stagnation to
enhance thrombus formation.
11. The vascular implant of claim 1, further comprising a tube
having a first end and a second opposite end, the first end seated
within coil windings of the helical coil.
12. The vascular implant of claim 11, wherein the tube is composed
of a metallic material different than a material of the helical
coil.
13. The vascular implant of claim 12, wherein the braid is melted
onto the tube.
14. The vascular implant of claim 12, wherein the tube has an
engagement structure extending proximally and external of proximal
coils of the helical coil.
15. A vascular implant for treating an intracranial aneurysm
comprising: an inner helical coil composed of a metallic material
and having a lumen formed therein extending from a proximal portion
to a distal portion, the metallic material being radiopaque; a
polymeric braid extending over and attached to the helical coil,
the braid having a distal opening, the braid extending along its
length to cover the proximal portion and the distal portion of the
helical coil, the braid formed by a plurality yarns, and the yarns
formed by a series of polymeric filaments, the braid configured for
inducing blood stagnation in the intracranial aneurysm of a patient
as blood enters the braid through the distal opening and through
spaces between the yarns and spaces between the filaments; and a
first radiopaque structure at a distal region of the vascular
implant to enhance radiopacity and extending into the braid and
having an opening to enable blood flow through the distal
opening.
16. The vascular implant of claim 15, further comprising a second
radiopaque structure spaced proximally from the polymeric braid and
having an opening to enable blood flow.
17. The vascular implant of claim 15, wherein the first radiopaque
structure is spaced proximally of the inner helical coil.
18. A vascular implant for treating an intracranial aneurysm
comprising: an inner helical coil composed of a metallic material
and having a lumen formed therein extending from a proximal portion
to a distal portion, the metallic material being radiopaque; a
polymeric braid extending over and attached to the helical coil,
the braid having a distal opening, the braid extending along its
length to cover the proximal portion and the distal portion of the
helical coil, the braid formed by a plurality yarns, and the yarns
formed by a series of polymeric filaments, the braid configured for
inducing blood stagnation in the intracranial aneurysm of a
patient; and a radiopaque structure at a proximal region of the
vascular implant proximal of the polymeric braid and inner coil to
enhance radiopacity and extending into the braid and having an
opening to enable blood flow through the distal opening.
Description
Technical Field
This application relates to medical devices, and more particularly,
to vaso-occlusive devices used in the treatment of intracranial
aneurysms.
Background of Related Art
An aneurysm is a localized, blood filled balloon-like bulge that
can occur in the wall of any blood vessel, as well as within the
heart. One endovascular treatment option for aneurysms is complete
reconstruction of the damaged vessel using a vascular prosthesis or
stent-graft. A stent-graft is an implantable tubular structure
composed of two parts, a stent and a graft. The stent is a
mesh-like structure made of metal or alloy which functions as a
scaffold to support the graft. The graft is typically a synthetic
fabric that is impervious to blood flow and lines the stent.
Stent-grafts are not a treatment option for intracranial aneurysms
due to the risk of cutting off blood flow to feeder vessels that
may be vital for brain function. Stent-grafts can also be stiff,
hard to deliver/retract, and can be highly thrombogenic within the
parent vessel, all of which are undesirable features for
intracranial aneurysm treatment. As a result, endovascular
treatment of intracranial aneurysms has centered on packing or
filling an aneurysm with material or devices in order to achieve a
high packing density to eliminate circulation of blood, which leads
to thrombus formation and aneurysm closure over time.
There have been a variety of materials and devices described for
filling the sac of an intracranial aneurysm such as injectable
fluids, microfibrillar collagen, polymeric foams and beads.
Polymeric resins such as cyanoacrylate have also been used. Both
are typically mixed with a radiopaque resin to aid in
visualization. These materials pose a significant risk due to the
difficulty of controlling dispersion and in retrieving them, if
improperly or excessively delivered.
Mechanical vaso-occlusive devices are another option for filling an
aneurysm. One type of mechanical vaso-occlusive device for the
placement in the sac of the aneurysm is a balloon. Balloons are
carried to the vessel site at the end of a catheter and inflated
with a suitable fluid, such as a polymerizable resin, and released
from the catheter. The main advantage of the balloon is its ability
to effectively fill the aneurysm sac. However, a balloon is
difficult to retrieve, cannot be visualized unless filled with
contrast, has the possibility of rupture, and does not conform to
varying aneurysm shapes.
Other types of mechanical vaso-occlusive devices are composed of
metals or alloys, and biocompatible fibers, for example. Generally,
the materials are formed into tubular structures such as helical
coils. One of the earliest fibered coils was the Gianturco coil
(Cook Medical). This coil was formed from a 5 cm length of 0.036''
guidewire (inner core removed) and featured four 2 inch strands of
wool attached to one tip of the coil to promote thrombosis. This
device was difficult to introduce into tortuous vessel sites less
than 3 mm in diameter. This is generally because the coil was stiff
or bulky and had a high coefficient of friction.
Chee et al. (U.S. Pat. No. 5,226,911) introduced a more deliverable
fibered coil with fibers that were directly attached to the length
of the coil body. This coil was designed for more tortuous anatomy
by decreasing the amount of thrombogenic material being delivered
with the coil. Other examples of coils are U.S. Pat. No. 4,994,069
to Ritchart et al.; U.S. Pat. No. 5,354,295 and its parent, U.S.
Pat. No. 5,122,136, both to Guglielmi et al.
Materials can also be formed into tubes/strings/braided sutures
(see, e.g., U.S. Pat. No. 6,312,421 to Boock; U.S. patent
application Ser. No. 11/229,044 to Sepetka et al.; U.S. patent
application Ser. No. 13/887,777 to Rees; U.S. patent application
Ser. Nos. 13/552,616 and 10/593,023 both to Wu et al.), cables
(see, e.g., U.S. Pat. No. 6,306,153 to Kurz et al.), or braids.
Metal coils can also be covered by winding on thrombogenic fiber as
described in U.S. patent application Ser. No. 12/673,770 to
Freudenthal and U.S. Pat. No. 6,280,457 to Wallace et al.
Unlike other tubular structures, braided or polymer coils can be
further divided into non-expandable and self-expandable devices.
These devices can be made from materials such as textiles,
polymers, metal or composites using known weaving, knitting, and
braiding techniques and equipment. Included in the weave or the
finished braid can be optional mono or multifilament fiber
manufactured to impart additional features or effects (e.g.,
radiopacity and thrombogenicity).
Non-expandable braids (see, e.g. U.S. Pat. No. 5,690,666 to
Berenstein et al.; U.S. Pat. No. 5,423,849 to Engelson et al.; and
U.S. Pat. No. 5,964,797 to Ho) can act as the implant and be mainly
metallic, polymer, or a combination of metal and polymer. In such
designs, braids have some minimal space between the filaments
(braid strands) resulting in open cell designs. In addition, tight,
mostly metal braids employing such designs result in stiff
structures which are difficult to track via catheter or risk injury
to the vasculature. Also, metal braided structures may be rough to
the touch if not covered or further processed.
These braids can be formed into secondary shapes, such as coils
that have little or no inherent secondary shape, they can be
dimensioned to engage the walls of the aneurysm, or they can have
other shapes (e.g. random, "flower", or three dimensional). These
structures can also have a fiber bundle(s) in, or protruding from,
the interior core made of natural fibers or thermoplastics infused
with drugs to help with clotting (see, e.g., U.S. Pat. No.
5,423,849 to Engelson et al.; and U.S. Pat. No. 5,645,558 to
Horton). Coiled braids can also be supplied with bio-active or
other surface coatings (see, e.g., U.S. Pat. No. 6,299,627 to Eder
et al.).
Non-expandable braids can also cover core or primary structures,
such as coils or other braids (see, e.g., U.S. Pat. No. 5,382,259
to Phelps et al.; U.S. Pat. No. 5,690,666 to Berenstein et al.;
U.S. Pat. No. 5,935,145 to Villar et al.; and U.S. Pat. No.
8,002,789 to Ramzipoor et al.). Much like the above braid
structures, these covers have open cell designs (e.g., inner coil
structure is visible through the braid).
Regardless of configuration, it is difficult to achieve high
packing densities and rapid flow stagnation with these devices as
they have open cell construction which allows at least some blood
flow through the wall, may not compress adequately, and/or may have
limited bend radii. If an aneurysm sac is not sufficiently packed
to stop or slow blood flow, any flow through the neck of the
aneurysm may prevent stasis or cause coil compaction, leading to
recanalization of the aneurysm. Conversely, tight packing of metal
coils in large or giant aneurysms may cause increased mass effect
(compression of nearby tissue and stretching of aneurysm sac) on
adjacent brain parenchyma and cranial nerves. Coil prolapse or
migration into parent vessels is another possible issue with
non-expanding devices, especially in wide neck aneurysms.
Braids may also be self-expanding and can be shaped into various
forms such as a ball, a coil(s), and a combination braid-stent.
Examples of self-expanding devices are disclosed in the following:
U.S. Pat. No. 8,142,456 to Rosqueta et al.; U.S. Pat. No. 8,361,138
to Adams; U.S. patent application Ser. No. 13/727,029 to Aboytes et
al.; U.S. patent application Ser. No. 14/289,567 to Wallace et al.;
U.S. patent application Ser. No. 13/771,632 to Marchand et al.; and
U.S. patent application Ser. No. 11/148,601 to Greenhalgh.
Self-expanding braids are expected to occupy all or substantially
all of the volume of an aneurysm to obstruct flow and/or promote
endothelization at the neck. A major problem for these designs is
sizing. The implant has to be accurately sized so that upon
expansion it occupies enough volume to fill the entire aneurysm,
dome to neck. Undersized devices lead to insufficient packing as
described above, whereas oversizing risks rupturing the aneurysm or
blockage of parent vessel.
Neck bridges are yet another approach to treating intracranial
aneurysms. They can be broken down into two categories: those that
act as support to keep the coil mass from migrating into a parent
vessel (coil retainer) and those that span the neck to obstruct
flow into the aneurysm. Neck bridges that support the coil mass
tend to be petal/flower shaped and span the neck of the aneurysm or
placed between the parent vessel and aneurysm sac. Examples of neck
bridges for supporting the coil mass are disclosed in the
following: U.S. Pat. No. 6,193,708 to Ken et al.; U.S. Pat. No.
5,935,148 to Villar et al.; U.S. Pat. No. 7,410,482 to Murphy et
al.; U.S. Pat. No. 6,063,070 to Eder; U.S. patent application Ser.
No. 10/990,163 to Teoh; and U.S. Pat. No. 6,802,851 to Jones et
al.
Neck bridges that obstruct flow through the aneurysm neck can be
deployed either internal or external to the aneurysm and may not
require deployment of embolization coils. Examples of
intra-aneurysmal neck bridges with deployment at the base of the
aneurysm sac with components extending into the neck are disclosed
in U.S. Pat. No. 6,454,780 to Wallace; U.S. Pat. No. 7,083,632 to
Avellanet et al.; U.S. Pat. No. 8,292,914 to Morsi; and U.S. Pat.
No. 8,545,530 to Eskridge et al. Examples of neck bridges deployed
external to the aneurysm (in the parent vessel) are disclosed in
U.S. Pat. No. 6,309,367 to Boock; U.S. Pat. No. 7,241,301 to
Thramann et al.; and U.S. Pat. No. 7,232,461 to Ramer; U.S. Pat.
No. 7,572,288 to Cox; U.S. patent application Ser. No. 11/366,082
to Hines; U.S. patent application Ser. No. 14/044,349 to Cox et
al.; U.S. Pat. No. 8,715,312 to Burke; U.S. Pat. No. 8,425,548 to
Connor; and U.S. Pat. No. 8,470,013 to Duggal et al. Neck bridges
can also have surface treatment to encourage neointima formation as
disclosed in U.S. Pat. No. 6,626,928 to Raymond et al. Regardless
of design, neck bridges pose several problems when treating
intracranial aneurysms. The first major challenge is deployment of
these devices, which requires the bridge to be maneuvered and often
re-positioned over the aneurysm neck to assure complete coverage.
Secondly, if recanalization occurs, any subsequent retreatment of
the aneurysm will be hampered due to access being restricted by the
neck bridge or one of its components.
Stents and flow diverters are similar to neck bridges in function,
but are intended for parent vessel reconstruction and therefore run
distal to proximal of the aneurysm, covering the neck. Such devices
are deployed in the parent vessel and are intended to act as a
physical blood flow barrier to induce sac embolization, stabilize
embolic coils, and prevent coil protrusion and/or migration. Flow
diverters, due to their relative low porosity (high coverage), can
be used with or without coils and have been found to promote
thrombus formation by restricting blood flow into the aneurysm sac.
However, complications such as recanalization, delayed stent
thrombosis, delayed aneurysm rupture, and stent migration have also
been observed. An example of a stent is disclosed in U.S. Pat. No.
6,746,475 to Rivelli and a flow diverter is disclosed in U.S. Pat.
No. 8,398,701 to Berez et al.
While the above methods attempt to treat intracranial aneurysms
with minimally invasive techniques, there remains a need for a
highly compliant and thrombogenic filler that blocks blood flow
within the sac of the aneurysm without the drawbacks of current
devices. For example, it would be advantageous to provide a device
that achieves sufficient flexibility to enable advancement through
the tortuous vasculature into the cerebral vasculature and achieves
high packing densities while maintaining a high concentration of
thrombogenic material. It would also be advantageous to provide
such device which is simple in structure and simple to manufacture
without sacrificing efficacy. Still further, since the device is
designed for minimally invasive insertion, such device needs to be
easy to deliver and deploy at the intracranial site as well as
manufacturable in a small enough size for use in cerebral
vasculature. All of this needs to be achieved with a construction
that effectively packs the aneurysm without damaging the sac or
other tissue while promoting rapid clotting and healing of an
intracranial aneurysm with reduction in mass effect. To date, no
device effectively achieves all these objectives, with current
devices at best achieving one objective at the expense of the
other.
SUMMARY OF INVENTION
The present invention provides an intra-aneurysmal micrograft that
overcomes the above discussed limitations and deficiencies in
treating aneurysms, especially intracranial aneurysms. The present
invention also provides intra-aneurysmal micrograft delivery
systems for delivering micrografts to an intracranial aneurysm.
In accordance with one aspect, the present invention provides a
vascular graft configured for occluding a vasculature of a patient
comprising: an absorbent biocompatible structure; and a core
element having a proximal end, a distal end and a lumen within the
core element, the core element positioned inside the biocompatible
structure and attached to the biocompatible structure; wherein a
capillary effect is created within the vascular graft when the
biocompatible structure is exposed to blood such that blood is
transported in a proximal direction through the vascular graft
wherein blood clots. In some embodiments, a lumen in the core
element is dimensioned to transport blood in a proximal
direction.
In some embodiments, the vascular graft is non-self-expanding. In
some embodiments, the core element has a coiled structure and the
graft further comprises a tube positioned within coils of the
coiled structure. In some embodiments the vascular graft has an
outer diameter less than 0.027 inches.
In some embodiments, the biocompatible structure is a textile
structure which includes a plurality of yarns spaced to wick blood
when placed in contact with blood. The plurality of yarns can each
be formed by a plurality of fibers, the fibers spaced to wick blood
when placed in contact with blood.
In some embodiments, the polymeric structure is crimped to form a
series of peaks and valleys along a surface of a wall to increase
flexibility
The vascular graft can include a radiopaque element within the
vascular graft. The vascular graft in some embodiments is shape set
to a non-linear configuration wherein it is movable to a
substantially linear configuration for delivery and returns to the
same or different non-linear configuration for placement within the
vasculature.
In some embodiments, the core element is made of a radiopaque
material. In some embodiments, the core element is wound into an
open pitch helical coil.
In accordance with another aspect of the present invention, an
occluding device for treating an intracranial aneurysm of a patient
is provided comprising an elongate tubular structure having a
plurality of yarns and a longitudinal axis extending in a distal to
proximal direction. The tubular structure is crimped to alter the
shape of the yarns and provide a first series of peaks defined by
the yarns and a first series of valleys formed between the yarns
and a second series of peaks and second series of valleys formed in
the tubular structure in a longitudinal direction to increase the
flexibility of the tubular structure.
In some embodiments, each of the plurality of yarns is formed by a
plurality of polymer filaments, the plurality of filaments having a
first set of pores (capillary spaces) therebetween for absorption
of blood to create a first capillary effect and the plurality of
yarns having a second set of pores (capillary spaces) therebetween
for absorption of blood to create a second capillary effect. In
some embodiments, the plurality of yarns and plurality of filaments
wick blood and the occluding device further has a lumen therein
through which blood can flow into to create a third capillary
effect. The lumen can include a distal opening for blood. In some
embodiments, the occluding device is shape set to a non-linear
configuration.
In accordance with another aspect of the present invention, a
system for occluding a vasculature of a patient is provided
comprising a vascular micrograft having an absorbent polymeric
structure, a lumen for passage of blood therein, an outer wall, and
a retaining structure attached to the vascular micrograft. A
delivery element has an engagement structure cooperating with the
retaining structure to retain the vascular micrograft during
insertion by the delivery element through the vasculature.
In some embodiments, the micrograft is positioned coaxially on the
delivery element.
In some embodiments, the retaining structure includes a radiopaque
marker band positioned within an internal portion of the vascular
micrograft and the engagement structure includes a taper on the
delivery element for frictionally engaging a proximal portion of
the vascular micrograft. In other embodiments, the engagement
structure includes a plurality of members movable from a first
expanded position to a second grasping position to grasp the
retaining structure. In some embodiments, the retaining structure
includes a tab movable between a first engaged position and a
second non-engaged position.
The system can further include a pusher catheter (member), the
delivery element extending through the pusher catheter, and the
micrograft having a diameter less than 0.027'' for delivery through
a microcatheter to an intracranial aneurysm.
In accordance with another aspect of the present invention, a
system for treating an aneurysm in a vessel of a patient is
provided comprising: an implantable occluding device configured for
introduction into a lumen of the vessel, the occluding device
having a first lumen for passage of blood therein; a delivery
member, the occluding device mounted on the delivery member such
that a portion of the delivery member extends into the first lumen
of the occluding device; and a catheter having a second lumen, the
delivery member extending through the second lumen; wherein
proximal movement of the delivery member exposes the first lumen
for passage of blood therethrough in a capillary action as blood
displaces the delivery member as the delivery member is withdrawn
proximally from the first lumen.
In some embodiments, the delivery member extends distally beyond
the occluding device during delivery of the occluding device to the
aneurysm. In some embodiments, the occluding device has a porous
outer wall.
In some embodiments, a clearance between an outer dimension of the
delivery member and an inner dimension of the occluding device is
substantially fluid-tight before delivery into the aneurysm but
sufficient to enable slidable movement of the delivery member with
respect to the occluding device.
In some embodiments, the delivery member is configured for delivery
through a catheter having a diameter less than or equal to
0.027''.
In some embodiments, the catheter has a distal portion in abutment
with the occluding device to advance the occluding device off the
delivery member into the aneurysm.
In some embodiments, the occluding device is a polymer structure
formed as a non-expanding braid composed of multiple multi-filament
yarns of polymeric material. In some embodiments, the polymer
structure is absorbent and wicks blood via a capillary action in a
distal to proximal direction.
In some embodiments, the occluding device includes retaining
structure engageable with an engagement structure of the delivery
member to retain the occluding device on the delivery member.
In some embodiments, the occluding device is shape set to a
non-linear configuration and advanceable from a substantially
linear configuration coaxially positioned on the delivery member to
the same or different non-linear configuration placed within the
aneurysm.
In accordance with another aspect of the present invention, a
method for treating an intracranial aneurysm is provided comprising
the steps of:
a) providing an occluding device having a lumen therein;
b) providing a delivery member;
c) inserting the delivery member with the occluding device into the
aneurysm, the delivery member retaining the occluding device during
delivery of the occluding device to the aneurysm;
d) retracting the delivery member proximally within the lumen of
the occluding device to provide a gap for blood flow in the lumen
of the occluding device; and
e) subsequently moving a pusher member to advance the occluding
device off the delivery member.
Preferably, the delivery member is inserted into a microcatheter
for delivery to the aneurysm.
In some embodiments, the occluding device is assembled of fibers
forming a fibrous structure.
In some embodiments, the delivery member is inserted into the
pusher member prior to advancing the delivery member through a
microcatheter to the aneurysm.
In some embodiments, the step of retracting the delivery member
includes retracting the delivery member until it is aligned with a
marker band attached to the occluding device.
In some embodiments, the occluding device is preset to a non-linear
configuration and advancement of the occluding device into the
aneurysm returns the occluding device from a substantially linear
configuration coaxially positioned on the delivery member for
delivery to the same or different non-linear configuration placed
within the aneurysm.
In some embodiments, the delivery member is a wire having a curved
or shaped tip.
In some embodiments, the step of inserting the delivery member
includes the step of passing the delivery member through a catheter
positioned in a stent in the vasculature. In some embodiments, the
occluding device can be guided within the aneurysm by the delivery
member.
In accordance with another aspect of the present disclosure, a
method for manufacturing a vaso-occlusive device is provided
comprising the steps of: a) braiding a series of multifilament
yarns over a mandrel to create a braid having an elongate body of
coaxially aligned filaments having a proximal portion, a distal
portion, and a lumen extending therebetween along a longitudinal
axis; b) compressing the elongated body longitudinally over the
mandrel until the elongate body buckles creating a sinusoidal shape
having a series of peaks and valleys along a length of the body and
bundles of individual filaments of the multifilaments within the
yarns orient substantially transversely to a longitudinal axis of
the mandrel to create a series of smaller peaks and valleys along
the length of the body; c) after step (b) heat setting the braid to
set the peaks and valleys; and d) removing the braid from the
oven.
In some embodiments, an internal stop extends from the body of the
device for cooperation with a delivery member. In some embodiments,
the step of braiding leaves pores between the series of
multifilament yarns.
The present invention also provides in some aspects methods for
filling and infusing an intra-aneurysmal micrograft with blood or
another liquid and delivering it to an intracranial aneurysm.
The present invention also provides in some aspects a system for
viscosity based retraction of intra-aneurysmal micrografts back
inside a catheter.
In one aspect, an intra-aneurysmal micrograft is provided having a
tubular body that has a textile construction with a through lumen
that has a series of peaks and valleys, or a wavy profile
(dependent on wall thickness), running longitudinally across its
length. At either end of the tubular body, bands can be provided
which may optionally be radiopaque and/or used for mating to a
delivery system. In another form of the construction, one or both
ends of the graft can be shape set with a "J" or curl or other
shape that help with delivery. In yet another form of the
construction, agents can be added to the inner or outer diameter of
the tubular body to aid in delivery (visualization), cancer
treatment and/or endothelial cell growth.
In some embodiments, the micrograft has a variable stiffness
tubular structure that has been shape set to have secondary shapes
such as a helical coil. The change in stiffness may be indicated by
a radiopaque marker band or reduced/compressed section. In some
embodiments, a single end or both ends of the micrograft can be
frayed to create Velcro-like locks that mate with other micrografts
sharing the same feature.
In some embodiments, the micrograft structure is formed to be
directable by blood flow. The micrograft may be cut longitudinally
and shape set to expose an inner surface or it may be a tubular
form. Additionally, the micrograft may have holes or slots.
In any of the foregoing, the micrograft can be formed using a
braided multi-filament polyester (e.g., PET) yarn, but it may be
formed of other flexible mono or multi-filament fibers, yarns, or
textile materials.
In one embodiment of a delivery system, a delivery wire with one or
more pre-mounted micrografts is inserted into an over-the-wire
pusher catheter having a through lumen. In some embodiments, the
delivery wire is a guidewire pre-mounted with one or more
micrografts. In yet another embodiment, the micrograft is loaded on
the primary guidewire used during a procedure. In some embodiments,
the pusher catheter is a rapid exchange catheter.
In one embodiment of the delivery system, a pusher wire with
grasper arms with bands engages a band, or thickened section, on a
proximal end of the micrograft inside a delivery tube.
In another embodiment of the delivery system, a push wire engages a
stent or flow diverter device which in turn engages a micrograft
inside a delivery tube.
In another alternate embodiment of a delivery system, a micrograft
is loaded into an introducer tube and used in combination with a
pusher catheter (member).
In accordance with one aspect of the present invention, a method of
placing and deploying a micrograft is as follows. A pre-loaded
delivery wire with a micrograft is loaded into a pusher catheter
(proximal end of wire loaded into distal end of pusher catheter)
until the distal end of the pusher contacts the micrograft. This
system is then advanced to an aneurysm through a microcatheter that
has been previously placed at the intended anatomical site. Once
the delivery wire and distal end of the micrograft reach the tip of
the microcatheter, the delivery wire tip is pulled back inside the
micrograft just distal of the lock. As the wire is drawn back,
blood fills the volume displaced by the wire inside the micrograft.
Once filled with blood, the delivery system is advanced until the
micrograft is deployed. When placed in the desired position, the
micrograft is detached by retracting delivery wire tip, or further
advancing pusher catheter, until the tip of the wire pulls through
the lock and into the pusher. In this method, as long as the wire
tip remains distal to the micrograft lock, the micrograft can be
retrieved. Once the micrograft is deployed, the delivery system is
removed and, if necessary, another pre-loaded delivery wire is
selected and the process for delivering a micrograft is repeated
until the aneurysm is sufficiently packed with micrografts.
In an alternate method, multiple micrografts are loaded onto a
single delivery wire. In some embodiments, instead of the delivery
wire, a standard guidewire is loaded with a micrograft of the
present invention during the procedure and the guidewire with
loaded micrograft can be used as a primary access wire. The pusher
catheter in an alternate embodiment is a rapid exchange
catheter.
In some embodiments of the delivery method, the micrograft is
directed for placement within the aneurysm using either a shaped
delivery wire or the microcatheter tip.
In some embodiments a micrograft is directed by blood flow once
released from the microcatheter.
In some embodiments of the delivery method, the proximal end of the
micrograft is locked by a series of arms extending distally from a
push wire that are compressed by advancing a loading tube. In such
method, to deliver the micrograft, the distal end of the loading
tube is inserted into a microcatheter luer and locked in place with
the Rotating Hemostatic Valve (RHV). The push wire with micrograft
is then advanced through the microcatheter until it reaches the
distal tip of the catheter. The micrograft is deployed by pushing
the arms of pusher wire out of the microcatheter so they can expand
and release the micrograft. The pusher arms can then be used to
move the micrograft around in the aneurysm or to grasp and retrieve
it. Like the previous method, this process can be repeated to
insert additional micrografts until the aneurysm is densely
packed.
In some embodiments of the delivery method, the micrograft is
delivered in tandem with a stent or flow diverter through a
microcatheter.
In some embodiments, a micrograft is pushed through a microcatheter
into an aneurysm without a delivery wire.
These and other features of the invention will become more fully
apparent when the following detailed description is read in
conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a side view partial cut away of an intra-aneurysmal
micrograft in accordance with one embodiment of the present
invention;
FIG. 2A is a view of another embodiment of the intra-aneurysmal
micrograft of the present invention having a larger diameter and
thinner wall;
FIG. 2B is a side view similar to FIG. 2A except showing the
micrograft stretched to highlight the peaks and valleys;
FIG. 2C is a side view of the micrograft of FIG. 2A in a bent
placement position;
FIG. 3A is a side view of another embodiment of the
intra-aneurysmal micrograft formed into a helical shape;
FIG. 3B is a side view of another embodiment of the
intra-aneurysmal micrograft having a flared end to be directed by
blood flow;
FIG. 4A is a side view partial cut away of an intra-aneurysmal
micrograft in accordance with another embodiment of the present
invention;
FIG. 4B is an enlarged view of one end of the micrograft of FIG.
4A;
FIG. 4C is side view of one end of an alternate embodiment of the
micrograft of the present invention;
FIG. 4D is a cross-sectional side view of the micrograft of FIG. 4A
placed over a mandrel before crimping;
FIG. 4E is a cross-sectional side view of the micrograft of FIG. 4D
after crimping;
FIG. 5A is a side view of an intra-aneurysmal micrograft delivery
system in accordance with an embodiment of the present
invention;
FIG. 5B is a side view of the delivery wire and mounted micrograft
of FIG. 5A;
FIG. 5C is an enlarged partial cross-sectional view of the
intra-aneurysmal micrograft of FIG. 5B showing the mating of the
micrograft with the taper of the delivery wire;
FIG. 5D is a side view of the pusher catheter of FIG. 5A without
the delivery wire;
FIG. 5E is a side view of an alternate embodiment of the micrograft
delivery system of the present invention;
FIG. 5F is an enlarged cross-sectional view of a portion of the
delivery system of FIG. 5E shown in the locked position;
FIG. 5G is view similar to FIG. 5F showing the delivery system in
the unlocked position;
FIG. 5H is a view similar to FIG. 5G showing the delivery system
withdrawn and the micrograft fully deployed;
FIG. 6 is a side view of a rapid exchange pusher catheter for
micrograft delivery in accordance with another embodiment of the
present invention;
FIG. 7 is a side view of another embodiment of the intra-aneurysmal
micrograft delivery system of the present invention having a pusher
wire with locking arms;
FIG. 8 is a side view of another embodiment of the intra-aneurysmal
micrograft delivery system of the present invention using a stent
or flow diverter to push the micrograft;
FIG. 9 is a side view of an intra-aneurysmal micrograft introducer
system in accordance with another embodiment of the present
invention;
FIG. 10 is a side view illustrating the loading of an
intra-aneurysmal micrograft delivery system of FIG. 5A into a
microcatheter;
FIGS. 11A-11F illustrate delivery of an intra-aneurysmal micrograft
into an intracranial aneurysm in accordance with an embodiment of
the present invention wherein:
FIG. 11A shows the delivery wire inserted into the aneurysm
sac;
FIG. 11B shows initial advancement of the micrograft into the
intracranial aneurysm after removal of the wire;
FIG. 11C is an enlarged cross-sectional view of the micrograft
exiting from the catheter corresponding to the position of FIG.
11B;
FIG. 11D shows the micrograft fully deployed from the catheter and
positioned in the intracranial aneurysm;
FIG. 11E is an enlarged cross-sectional view of the deployed
blood-filled micrograft corresponding to the position of FIG.
11D;
FIG. 11F shows multiple micrografts of FIG. 11E positioned in the
intracranial aneurysm sac;
FIGS. 12A-12C illustrates directed delivery by the delivery wire of
an intra-aneurysmal micrograft into an aneurysm in accordance with
an embodiment of the present invention;
FIG. 13 illustrates delivery of smaller length flow directed
intra-aneurysmal micrografts into an intracranial aneurysm in
accordance with another embodiment of the present invention;
FIG. 14 illustrates delivery of the delivery wire carrying the
intra-aneurysmal micrograft through cells of a stent or flow
diverter into an aneurysm in accordance with another delivery
method of the present invention;
FIG. 15 illustrates delivery of an intra-aneurysmal micrograft into
an aneurysm using a delivery wire with the arms of FIG. 7;
FIG. 16A is a photograph of an uncrimped tubular PET braid
alongside a crimped braid of the present invention to show a
wave-like profile as in FIG. 1A;
FIG. 16B is a photograph of a crimped micrograft braid alongside a
crimped micrograft braid that has been heat set into a coiled shape
in accordance with an embodiment of the present invention;
FIG. 16C illustrates a micrograft tubular body of the present
invention partially filled with a fluid to illustrate the capillary
effect.
FIG. 17 is a photograph of one end portion of the micrograft of
FIG. 1A;
FIGS. 18A and 18B are flowcharts summarizing alternate methods of
placing and deploying a micrograft of the present invention;
and
FIG. 19 is a flowchart summarizing viscosity lock function in
accordance with an embodiment of the present invention.
DETAILED DESCRIPTION
The following embodiments are described in sufficient detail to
enable those skilled in the art to practice the invention, and it
is understood that structural changes may be made without departing
from the scope of the present invention. Therefore, the following
detailed description is not to be taken in a limiting sense. Where
possible, the same reference numbers are used throughout the
drawings to refer to the same or like components or features.
FIG. 1 illustrates a partial cut away side view of an
intra-aneurysmal micrograft for insertion into an intracranial
aneurysm in accordance with one embodiment of the present
invention. The micrograft of this embodiment, designated generally
by reference number 10, includes a biocompatible
non-self-expandable absorbent braided polymeric textile tubular
body 12 that has been crimped to reduce stiffness and increase wall
thickness and fabric density. The micrograft 10 has sufficient
stiffness as well as sufficient flexibility to provide the
advantages described below. It further is structured to enable a
triple capillary action to promote blood clotting as also discussed
in detail below. The micrograft further preferably has a high
surface area for increased blood absorption, is radially
deformable, has a low friction surface for ease of delivery and can
be shape set to enhance packing of the aneurysm. These features and
their advantages are described in more detail below. Note the
micrografts of the present invention are especially designed to
induce blood stagnation or clot to rapidly treat the aneurysm. The
micrografts are configured for delivery to an intracranial
aneurysm, although they can be utilized for occlusion in other
aneurysms in other areas of the body as well as for occlusion in
other vascular regions or in non-vascular regions.
An over the wire delivery system is provided to deliver the
micrograft of the present invention to the aneurysm. Variations of
these delivery systems of the present invention are discussed in
detail below. Preferably, multiple micrografts are delivered so
that the aneurysm sac is densely packed.
Turning first to the biocompatible micrografts of the present
invention (the delivery systems are subsequently discussed) the
preferred tubular body 12 of micrograft 10 is constructed of
substantially 100% 20 denier/18 filament polyester (e.g., PET)
multi-filament interlaced yarns, but can be made of other
combinations of denier and filament such as 10 denier/16 filament
yarn, or 15 denier/16 filament yarn, for example. That is, each
yarn is composed of a plurality of polyester filaments having pores
or spaces therebetween, and the plurality of yarns also have pores
or spaces therebetween, for reasons described below. The tubular
body has a proximal end 14 and a distal end 16, with proximal
defined as closer to the user and distal defined as further from
the user such that the distal end is inserted first into the
aneurysm. Blood then flows through the micrograft 10 in a distal to
proximal direction. The tubular body 12 has a preferred inner
diameter in the range of about 0.001 inches to about 0.068 inches,
and more narrowly in the range of about 0.006 inches and about
0.040 inches, for example about 0.008 inches. It has a length
ranging from about 2 mm up to about 150 cm and a preferred outer
diameter in the range of about 0.002 inches to about 0.069 inches,
more narrowly in the range of about 0.010 inches to about 0.041
inches, for example about 0.010 to about 0.020 inches. Note that
although these ranges and dimensions are the preferred ranges and
dimensions, other ranges and dimensions are also contemplated.
These dimensions provide a sufficiently small size micrograft so
that the micrograft can be navigated to and into the cranial
vasculature for placement within a cranial vessel.
Each of the multi-filament yarns are made of multiple wettable
micro-filaments, or fibers, assembled with spaces (pores) between
them, referred to as inter-fiber spaces or pores. The pores are
sufficiently sized to induce capillary action when contacted by a
liquid, resulting in the spontaneous flow of the liquid along the
porous yarn (i.e., wicking). This capillarity between fibers
(intra-fiber) within the yarn is termed as "micro-capillary"
action. As a result, a sufficiently wettable and porous yarn will
have high wickability and transport liquid along its length. The
multiple filaments also provide a high surface area and can be
hydrophilic or hydrophobic.
This assembly of the two or more wickable multi-filament yarns into
a permeable structure (such as a textile) results in a
"macro-capillary" action, i.e., the transporting of liquid between
the yarns and throughout the structure. Such yarns and/or fibers
can be textured, flat, twisted, wettable, non-wettable, with beads,
of various cross-sections (tri-lobal, multi-lobal, hollow-round,
etc.), coated or having a modified surface, composite, reticulated,
porous, pre-shrunk, crimped or modified using similar heat
treatment or chemical processes.
The multi-filament yarns can be assembled into a textile tubular
structure using a braider or other textile manufacturing equipment
and methods. In general, the braider can be set-up with a program
or recipe, spools of multi-filament yarn and an optional core
mandrel to braid over. Anywhere from about 8 to about 288 strands
of multi-filament yarn may be used to form the tube, depending on
the desired final structural properties such as density, picks per
inch (PPI), porosity, compliance, etc. If desired, multiple
braiders or a braider in combination with a coil winder can be run
simultaneously to form a braid over braid or braid over coil
design.
The micrograft 10 is braided over the core mandrel which sets the
internal diameter (ID) of the braid. The core mandrel can be made
of a variety of materials such as metal, wire, polymers or other
textile fibers. It can also be formed of a stretchable material to
aid in removal during manufacturing.
The micrograft 10 can also include a permanent core element such as
shown in the embodiment of FIG. 4A discussed below. The core
element can be made of a variety of materials, and can itself be
formed of one or more filaments, and may optionally be coated. In
one embodiment, the core element is formed of a metal coil having a
lumen therein. It can be composed of platinum-iridium or other
materials. The braid and coil can be heat set at a temperature that
would not damage or disintegrate the braid.
The braiding process may be adjusted for the highest PPI possible
so as to produce a tightly interlaced, dense braid without tenting
(braiding over itself or overlapping). However, in some cases
tenting may be desirable to produce a useable feature such as a
braid bulge or ring for locking or wall thickening. The braid,
while still mounted on the core mandrel, may be heat treated after
manufacturing to set the braid structure, including PPI, and to
relieve filament stresses produced during braiding.
The preferred PPI for the as-braided therapeutic structure, for
example, may range from about 80 to about 200 PPI for a 16 strand
braid, and more narrowly in the range of about 120 to about 180
PPI, preferably about 167 PPI. The PPI is dependent on the number
of strands used to braid, the braid angle, and the braid diameter,
such that a braided tube of a given diameter with 120 PPI and 16
strands would have a PPI of 60 when braided using 8 strands at the
same diameter (assuming all of the variables constant). The
preferred PPI should be high enough to produce a dense interlacing
pattern, but not so high as to interfere with core mandrel removal,
unless the core is stretchable. Crimping, which will be discussed
later in detail, may be used to increase PPI (and braid angle),
once again depending on final structural requirements.
The use of multi-filament yarns in combination with a relatively
high PPI of the present invention results in a somewhat stiff,
relatively small or closed cell (high pick density) braided tube.
As mentioned above, there is a micro-capillary effect resulting in
wicking of liquid along the porous yarns due to inter-fiber spaces
and a macro-capillary effect resulting in liquid flow between yarns
and throughout the textile wall due to inter-yarn porosity
associated with using a wettable multi-filament yarn. Due to the
manufactured tube's relatively small inner diameter and a
sufficiently dense interlacing braid pattern (i.e., a filamentary
wall structure with sufficiently small pore size such that it
retains fluid), a third capillary effect is created. When properly
sized, this third capillary effect is responsible for spontaneous
flow of liquid inside the micrograft lumen, e.g., within the lumen
of the braid, in a proximal direction. The liquid can also spread
in other directions as it is absorbed. This structure thus results
in a soft capillary tube that has absorbent walls. This triple
capillary effect is beneficial for a vaso-occlusive device due to
the fact that the yarns, the fibrous wall, and the micrograft lumen
can become saturated with blood. Since blood absorbed by the
micrograft is trapped within the structure, it becomes stagnant and
will quickly thrombose or form clot.
To achieve the capillary and clotting characteristics, the
micrograft 10 achieves an optimal balance of porosity and fluid
containment within the same structure. This is achieved by
controlled interlacing of microporous yarns that allow blood
wicking and cell ingrowth. When braided with sufficiently high PPI
and tension, for example, the porous yarns are able to form a fluid
barrier that maintains a degree of permeability. The resultant
structure (textile tube) is an assembly of micro-porous yarns that
may be interlaced with sufficient density to form a fluid-tight
tubular capillary. This interlacing of the yarns or assembly of
filaments can be achieved using textile manufacturing processes,
such as weaving, knitting, or electrospinning. Porous or
semi-porous filaments may also be used in place of multi-filament
yarns to achieve desired absorbency. Additionally, the micrograft
structure does not have to include a clearly defined inside lumen
to maintain capillarity, e.g., a defined lumen formed within the
wall of the braid or core element, but may alternatively be a
porous assembly of fibers sufficiently spaced to allow transport of
liquid (much like a suture or string wicking liquid) or a porous
scaffold or biocompatible open cell foam.
While the semi-porous micrograft 10 as formed as described above
has the desired effect of aiding thrombus formation, it is also
relatively stiff as a result of the filaments being closely packed
or tightly braided as mentioned above. One benefit of a stiff,
denser braid is its ability to retain its non-linear heat-set shape
as compared with lower PPI (less dense) braids. This may facilitate
the use of stiffer, higher density 3D shaped micrografts as
framing-type devices used for initial filling of aneurysm
circumference, and then soft and highly compliant micrografts may
be used as fillers or "finishing" devices towards the end of the
embolization procedure. For example, a dense (or high PPI)
2.times.2 (two-over-two) configuration braid may be used as the
initial "framing" device whereas a softer and more compliant braid
having a lower-PPI 1.times.2 (1-over-2-under-2) configuration braid
may be subsequently used to fill the framed space within the first
device. However, even if used as a framing device, excessive
stiffness is an undesirable mechanical property for the
microcatheter delivery because an overly stiff device may cause
unwanted movement of the microcatheter tip during delivery which
can adversely affect navigation of the microcatheter or damage
vessels during advancement through the tortuous vasculature.
Excessive stiffness is also an undesirable property because stiff
devices will conform less to the configuration of the aneurysmal
sac and thus prevent efficient aneurysm packing.
Therefore, to reduce stiffness to assist delivery and packing of
the aneurysmal sac, the micrograft tubular body (braid) 12 is
crimped during manufacture, i.e., longitudinally compressed and
heat set. As the braid 12 is compressed, axial orientation of the
braided strands is reduced thereby increasing braid angle with
respect to the longitudinal axis of the tubular body which reduces
their influence on overall stiffness of the structure, much like a
straight wire taking on a more flexible form when coiled. Crimping
will also effectively increase the PPI, wall thickness, and linear
density of the braid by axially compressing the structure and
filament bundles. This compression causes an outward radial
expansion and an increase in wall thickness of the tube. The
resulting braid is much more deflectable, has reduced bend radius,
a higher density and up to 2.times. to 3.times. or higher increase
in PPI, depending on braid structure and compressive force
applied.
This axial compression also causes the braid structure to "snake"
or produce a spiral wavy form as shown in FIG. 1, which as viewed
from the side is a series of macro peaks and valleys, termed
"macro-crimps" in a sinusoidal shape. The sinusoidal undulations
(macro-crimps) are typically more pronounced in braid structures
where the ratio of wall thickness to overall braid diameter is
larger (i.e., overall diameter decreases). Sufficient crimping may
also re-orient individual yarn fiber bundles from a mostly
flattened (longitudinally organized cross-section) state to a
compressed (transversely organized cross-section) state. This
increases surface unevenness of the braid since individual yarns
bulge outward and produce micro peaks and valleys on the braid
surface, termed "micro-crimps" (see FIG. 4B for example) with the
peaks 17 located at the height of the yarn and the valleys 19
between adjacent yarns.
The braid can have a series of coaxial aligned filaments and
compressed so the filaments orient substantially transversely (with
respect to a longitudinal axis of the mandrel).
Different braid patterns (such as 1.times.1, 1.times.2, or
2.times.2, etc.) may also produce varied results when crimped. For
example, a 1.times.1 braid structure will tend to have a more
uniform tubular shape and less distinctive macro-crimp pattern,
whereas a 1.times.2 braid structure will produce a more sinusoidal
(macro peaks and valleys) crimped structure in addition to the
micro peaks and valleys (micro-crimps) of individual fiber bundles.
These structural changes result in an ultra-deflectable, increased
density, wavy-wall structure having macro-peaks 18 and valleys 20
as shown in the sinusoidal shape of FIG. 1A.
Besides increasing braid flexibility, PPI and/or wall thickness,
varying amounts of crimping imparts other potentially desirable
features such as kink and crush resistance, reduced bend radius, as
well as increased surface area per unit length via accordion-like
compression of the wall (i.e., forming peaks and valleys). The
uneven texture of crimped peaks and valleys also helps create
localized hemodynamic turbulence and flow stagnation, resulting in
improved thrombus formation. The crimps make the device more
compliant, easily deflectable and conformable which facilitates
packing confined spaces or voids in the vasculature, e.g., the
aneurysm. Crimping may also be used to vary wicking and
permeability of the textile wall since it reduces fabric porosity
and increases yarn tortuosity.
The location, amount and magnitude of crimping can be controlled to
impart different amounts of flexibility and elongation to the
structure to achieve its desired characteristics. For example,
extreme crimping can be applied so the braid is compressed until
the individual fibers within each yarn bundle come together and
cannot compress any further, giving the braid some rigidity and
improving pushability through a microcatheter lumen. Other factors
that impact crimping and the resulting longitudinal pattern are
fiber diameter and stiffness, yarn tension during braiding, wall
thickness, wall porosity (PPI), number of filaments, and mandrel
diameter.
For example, larger diameter, thin walled tubular bodies (braids),
i.e., low wall thickness to outer diameter ratio, may show macro
peaks and valleys which are more dense and visible than small,
thick walled crimped tubes. FIGS. 2A-2C show an example of such
large diameter thin walled tube where crimping can form an
accordion-like folds or pleat structure rather than a sinusoidal
configuration as the peaks are closer together. Crimping smaller
diameter braids (braids with higher wall thickness to outer
diameter ratios) typically induces a wave-like, sinusoidal
longitudinal (macro) contour that is larger in comparison to
overall diameter and increases wall thickness of the structure, as
shown in FIG. 16A. It should be noted the sinusoidal contour is
typically three-dimensional in form (like a spiral) and is visible
from all sides of the braid. During crimping, the ends of the
tubular body may also be rotated/twisted relative to each other and
then heat set as another method to impart deflectability to the
tubular body.
The braid 10 can also be made more flexible by varying the braid
angle or PPI, by reducing yarn tension, by adding cuts/slits,
changing the number of filaments or strands, or heat setting
repeating patterns along its length (such as flat sections or
kinks). If a stiffer tube is desired, denser yarn and/or braid
pattern may be used or crimping decreased. Additionally, the
micrograft structure may incorporate a coaxial construction (i.e.,
having a graft inside a graft) or multi-ply or multi-lumen wall
design, especially when using fine-denier textiles. Intra-luminal
braid inserts, such as the coils mentioned above, may also be
composed of, or coated with, a highly wettable/hydrophilic material
to enhance the capillary effect. For example, the micrograft may be
coaxially assembled with a secondary braid or internal coil
structure that is highly hydrophilic and/or radiopaque, while
maintaining the therapeutic external surface.
The tubular body 12 may be braided, woven or knitted, partially or
completely, from monofilaments or multi-filament yarns, strands,
sutures, microfibers, or wire that is synthetic, semi-synthetic,
natural or thermoplastic. Such materials may include, but are not
limited to, Dacron, poly ester amide (PEA), polypropylene, olefin
polymers, aromatic polymers, such as liquid crystal polymers,
polyethylene, HDPE (high density polyethylene),
ultra-high-molecular-weight polyethylene (UHMWPE, or UHMW),
polytetrafluoroethylene (PTFE), ePTFE, polyethylene terephthalate
(PET), polyether ketone (PEK), polyether ether ketone (PEEK), poly
ether ketone ketone (PEKK), nylon, PEBAX, TECOFLEX, PVC,
polyurethane, thermo plastic, FEP, silk, and silicone,
bio-absorbable polymers such as polyglycolic acid (PGA),
poly-L-gllycolic acid (PLGA), polylactic acid (PLA), poly-L-lactic
acid (PLLA), polycaprolactone (PCL), polyethyl acrylate (PEA),
polydioxanone (PDS) and pseudo-polamino tyrosine-based acids,
extruded collagen. Metallic, metallic alloy or radiopaque material
may also be included, Such material may be in the form of strands
or filaments and may include, for example, platinum, platinum
alloys (platinum-iridium or platinum-gold, for example), a single
or multiple stainless steel alloy, nickel titanium alloys (e.g.,
Nitinol), barium sulfate, zinc oxide, titanium, stainless steel,
tungsten, tantalum, gold, molybdenum alloys, cobalt-chromium,
tungsten-rhenium alloys.
The use of different manufacturing methods or materials to
construct the tubular body may have an impact on the capillary
effects discussed earlier. For example, a change in material or
construction methods may result in a simple capillary tube with
capillary flow restricted to only the inner lumen of the tube, and
not the walls. It should be understood by those skilled in the art
that strands or filaments may be braided, interwoven, knitted, or
otherwise combined to form a fabric or textile structure.
With reference now to the drawings showing exemplary embodiments of
the micrograft of the present invention, the micrograft 10 of FIG.
1, as discussed above has a tubular body 12 with a proximal end 14
and a distal end 16.
To provide radiopacity so the device is visible under fluoroscopy
(x-ray), the micrograft 10 can include radiopaque marker bands 22
which are inserted into the ends of the micrograft 10. FIG. 17 is a
picture of an end of micrograft 10 with such marker band. The
marker bands, which can also be in the form of coils, can be made
from tantalum, platinum, platinum alloys (e.g., platinum-iridium
alloy), gold, tungsten, or any suitable radiopaque material such as
radiopaque polymer. The marker bands 22 are preferably
approximately 1 mm or less in length and can be either of a
sufficient inner diameter to slide over tubular body 12 or of a
smaller diameter to fit inside the tubular body 12. FIG. 1 shows an
example of the marker bands 22 fit inside the tubular body and the
marker bands 22 can be secured by melting of the braid over the
bands (the melted fiber) at region 24, or attached by gluing. The
bands 22 can also be undersized and sliced lengthwise so that they
can be swaged or folded over the outside of tubular body 12, or
tubular body 12 can be stretched so that undersized bands can be
slid over the stretched/compressed length in order to attach the
bands 22 to the tubular body 12. In alternate embodiments, the
bands can be flared at one end.
Although two marker bands are shown, in alternate embodiments,
there may be one band or more than two bands placed around the
tubular body along portions of its length to improve radiopacity.
The bands positioned along the length can be in lieu of or in
addition to a marker band at one end or a marker band at both ends.
A radiopaque fiber can be utilized to connect the bands, and the
radiopaque fiber incorporated into the textile structure, or placed
inside the tube. The bands can be composed of metal, or
alternatively of a non-metallic material such as radiopaque shrink
tubing or polymer.
The marker bands can be adhered to the tubular body 12 using
adhesive, mechanically by swaging or winding directly on to the
tubular body, or by heating (when possible) and melting one of the
materials. The bands can alternatively be attached by being screwed
onto or into the core element, e.g., a helical core element, as
discussed below.
As an alternative or in addition to the marker bands, radiopacity
can be obtained by coating, wetting, staining, or impregnating the
micrograft with a radiopaque material such as contrast media
solution or nanoparticles. This can be done in manufacturing or in
the operating room as part of the clinical procedure. The fibers or
yarns themselves may be doped or impregnated or coated with
radiopaque substances as described above. The micrograft may also
contain a series of equally spaces radiodense inserts along its
length, resulting in intermittent radiopacity which may be
sufficient for visualization in clinical settings.
In addition to providing radiopacity, bands 22 can also be used to
indicate structural changes in tubular body 12, as a means to
control fraying, or as an integral part of the delivery system
(e.g., stop-collar) as will be better understood in the discussion
below of the delivery of the micrograft.
As another alternate to the bands, laser cut Nitinol structures
that are made increasingly radiopaque can be utilized. These
structures can be glued, melted over, sewn or otherwise attached to
the proximal and/or distal ends of the micrograft, either on the
inner or outer diameter, and/or attached along a length of the
tubular body. Sections of the micrograft or meltable/fusible
sleeves of a braided polymer may also be heated and used to adhere
bands or other radiopaque structures (components) to the
micrograft. Bands or other radiopaque components can alternatively
be attached by screwing into the coil windings inside the braid.
The bands or other radiopaque components can either be
self-expanding or non-self-expanding. When mated with the delivery
wire and pusher catheter described below, they can serve to control
micrograft linear movement relative to the wire.
As an alternative to the bands for providing radiopacity, a
radiopaque agent as described above could be utilized which would
allow complete visualization of the full length of the graft.
Another way to provide visualization is the inclusion of a
radiopaque coil or insert across the entire length of the inner
lumen of the micro-graft. The addition of such coil would make the
entire length of the graft radiopaque, however, preferably, to
avoid such coil adding an unwanted increase to the structure's
radial stiffness, and to minimize such stiffness while maximizing
x-ray visibility, such coil may be wound using very thin wire
typically not visible via fluoroscopy, but when coiled with
sufficiently small pitch (spacing between each loop) it becomes
increasingly dense and visible. Pitch of the coil may also vary to
make some sections more radiopaque or flexible than others. The
coil can be made of materials such as platinum, platinum-iridium,
tantalum, gold, silver or other radiopaque materials used for
medical device visualization. The coil can have a continuous
diameter or variable diameter along its length, depending on use.
The coil can also be used in combination with radiopaque bands,
coatings or as a stand alone radiopaque solution. Insertion of such
coils inside the micrograft may also reduce the amplitude of
macro-crimps formed during crimping if desired, depending on radial
apposition of coil to braid. It should also be noted that coils or
other internal inserts may be partially visible through the braid
wall depending on the amount of crimping.
If needed, a simple "J" shape can be heat set into tubular body 12
to aid with introduction into the aneurysm. Agents may also be
added to the tube to aid in delivery and/or endothelial cell
growth. For example, a hydrophilic coating can be applied to the
surface of tubular body 12 to aid in delivery through a
microcatheter or a swellable hydrogel infused with drugs can be
added to provide medicinal treatment and additional filling of the
aneurysm. Another example is a clotting agent which may be added to
either slow or inhibit the clotting process or to promote clot
formation. Bio-absorbable and biocompatible fibrous elements such
as Dacron (polyethylene terephthalate), polyglycolic acid,
polylactic acid, a fluoropolymer (polytetrafluoroethylene), nylon
(polyamide) or silk can also be incorporated into the braid, or to
the surface, to enhance the ability of the tubular body 12 to fill
space within the vasculature and to facilitate clot formation and
tissue growth. Similarly, hydrogels, drugs, chemotherapy beads
and/or fibers can be added to the inner diameter of tubular body 12
or infused into the walls, yarns, or fibers depending on specific
use (for example embolic chemotherapy). On the finishing side of
the micrograft (proximal end), a microcoil (not shown) may be added
to provide a barrier between the aneurysm sac and the parent
vessel. FIG. 1 can include similar features or functions as will be
described below.
FIGS. 2A-2C illustrate a micrograft similar to micrograft 10 of
FIG. 1 except having a larger diameter and thinner wall. FIG. 2A
illustrates the thin walled micrograft 25 crimped in the process
described above to forms peaks and valleys resulting in
circumferential corrugations or folds. FIG. 2B is provided for
illustrative purposes to highlight the peaks and valleys by
stretching the tubular body. FIG. 2C shows a portion of the
micrograft 25 in the bent position. In some embodiments, the
micrograft is pre-set in this bend, e.g., a U-shaped configuration,
to improve packing within the aneurysmal sac. As shown, due to the
structure of the micrograft, when bent, it maintains its radius in
the similar manner to a bent coil. (The micrograft would be
delivered in a substantially linear position as described below).
As shown, the compression and heat setting (crimping) process
creates an "accordion like" structure with peaks 18' and valleys
20'. In FIGS. 2A-2C, the wall of the micrograft 25 is a fine braid,
or textile structure, and will approximate a solid structure when
placed in direct blood flow, causing high flow disruption. Another
feature of the graft is its white color, which may vary depending
on PET formulation and processing. If desired, colors other than
white may be used to denote different body diameters or transitions
in mechanical or therapeutic properties, for example.
FIGS. 4A, 4B, 4D and 4E show an alternative embodiment of the
micrograft 10'. Micrograft 10' is similar to micrograft 10 as it
formed from a braided tube 12' and has the same features and
functions of tube 12 as well as can include any of the alternate
constructions described herein. Thus, the various descriptions
herein of the filaments, yarns, capillary effects, shape set, etc.,
are fully applicable to the micrograft 10' of FIG. 4A. However,
micrograft 10' has a core element 27, preferably formed by a
helical coil, having a lumen for blood flow in the aforementioned
capillary effect. A tube 29, preferably composed of Nitinol,
although other materials can be utilized, is seated within proximal
coils of the tube 29, preferably screwed or twisted into the coil
windings of the helical core element 27. The braid is melted onto
tube 29, with region 24 showing the melted fibers, to attach the
tube 29. Tube 29 has a deflectable tab 29a and a window 29b to
receive a delivery wire as described below in conjunction with the
delivery method. The tab 29a is biased to the aligned position of
FIG. 4B and is moved to an angled position to receive the wire
through the window 29b, the tab 29a providing an
engagement/retaining structure for engagement with a wire of a
delivery system described below. Braided tube or braid 12' is made
up of yarns 31 each containing multiple fibers 33. When removed
from the braider, the yarn(s) 31 of tube 12' will lay relatively
flat with the fibers 33 bundled horizontal and spaced apart (see
FIG. 4D showing tube 12' positioned over mandrel 35). FIG. 4E
illustrates the braided tube 12' which has been crimped over
mandrel 35 to create crimped braided tube 12' prior to formation
into the structure of FIG. 4A. When the braid is fixed to the
mandrel 35 at one or more points and a longitudinal force is
applied to the braid, the fibers 33 in the yarn 31 will move closer
together and bundle vertically creating micro peaks 17 and micro
valleys 19 (between peaks 17) and corresponding macro peaks 18 and
macro valleys 20 along the tube length creating a sinusoidal shape
(FIG. 4E). (The peaks and valleys of the FIG. 1 embodiment
disclosed herein can be formed in a similar manner). The extent of
the peaks and valleys is dependent on the amount of force applied
and the desired amount of softness. The tube can be completely
crimped or selectively crimped at intervals along its length.
In the alternate embodiment of FIG. 4C, instead of a locking tab, a
marker band 22' is attached to the tube to provide retention
structure for engaging structure on the delivery wire. In all other
respects, the micrograft of FIG. 4C is the same as the micrograft
10' of FIG. 4A and has therefore been labeled with the same
reference numerals.
FIG. 3A illustrates another embodiment of an intra-aneurysmal
micrograft. A variable stiffness micrograft 26 with tubular body 28
includes the same features and functions as described above with
respect to FIG. 1, or its alternatives, e.g., multifilament yarns,
capillary effects, etc. However, in this embodiment, the micrograft
26, after forming and crimping, is wound about a mandrel to form a
secondary coil shape as shown. This is also shown in FIG. 16B
wherein the micrograft 26 is pictured both after braiding and
crimping (still straight) and after it's wound into a coil after
formation of such braided and crimped structure. Other micrografts
described herein, with the varying features described herein, can
also be wound into a coil shape of FIG. 3A if desired. The tubular
body 28 of micrograft 26 is composed of a variable stiffness braid
having a proximal stiff section 30 and a distal flexible section
32, the varying stiffness achieved in the ways described above.
Tubular body 28 also has a primary diameter D. A radiopaque band 36
can be provided to allow visualization under fluoroscopy and is
shown in the approximate center of the braid where it transitions
in stiffness. The radiopaque band 36 can alternatively be
positioned in other locations and multiple bands can be provided.
Alternatively, radiopacity can be achieved in the various ways
described above.
Device 26 is shape-set with heat in a pre-biased (secondary)
helical shape of FIG. 3A (and 16B.) This is the delivered shape-set
form of the device 26. This device may not have such pronounced
peaks and valleys as micrograft 10 due to the stretching, bending
and heating needed to form secondary shapes. However, the original
crimping operation induces the desired properties and makes the
micrograft more compliant. Partial stretching or partial un-doing
of the crimping also results in a braided lumen that is more
compliant radially for improved packing.
Although shown helically-shaped, device 26 can be shape set into
any complex three dimensional configuration including, but not
limited to, a cloverleaf, a figure-8, a flower-shape, a
vortex-shape, an ovoid, randomly shaped, or substantially spherical
shape. As mentioned earlier, a soft, open pitch coil can be added
to the inner diameter of the braid to aid in visualization. If
stiffness of such metal coil is sufficiently low, the secondary
shape-set of the polymer braid will drive the overall shape of the
device. In other words, the secondary shape of the braid molds the
unshaped metal coil which normally shape sets at temperatures much
greater than the glass transition temperature of polymers.
The micrograft 26 also has frayed end fibers 38 shown on one end of
the device. These loose frayed fibers can alternatively be on both
ends of the braid, if desired (other micrografts disclosed herein
could also have such frayed ends). When these frayed ends come in
contact with another braid within the aneurysm sac having the same
feature, the mating ends act like Velcro, allowing the micrografts
to interlock and move together. For delivery and introduction into
catheter, device 26 would be elongated, e.g., moved to a
substantially linear configuration, and inserted into a loading
tube having an inner diameter of sufficient size to accommodate
primary diameter D. An optional filament (not shown) may extend
from the proximal end of the braid to allow pinching/anchoring of
the micrograft between a stent or flow diverter and the parent
vessel wall upon release to obstruct flow at the aneurysm neck.
Packaging and delivery is discussed in detail below.
FIG. 3B illustrates another embodiment of an intra-aneurysmal
micrograft. Sliced micrograft 40 has a tubular body 42 that can
include the same features and functions as described above for the
previous embodiments, e.g., multifilament yarns, capillary effects,
etc. Tubular body 42 has a longitudinal cut 44 and is shape set to
expose its inner surface 46, thereby providing a flared distal end.
Micrograft 40 is configured with a portion of the inner diameter
exposed to maximize surface area constricted by flowing blood and
to aid in movement with blood flow. Device 40 can include a
proximal marker band 48 (or alternatively any of the other
aforedescribed radiopaque features) for visualization. Holes 50 and
52, formed by laser cut or other methods, provide for communication
with the blood. Micrograft 40 is particularly suited for placement
at the neck of the aneurysm either manually with a delivery system
or through movement with blood flow circulating within the
aneurysm. Delivering micrografts 46 to an aneurysm may result in
clogging at the neck/stent interface as they get caught up in
exiting blood flow and accumulate at the aneurysm neck. This
structure can also be a round tube, flattened tube, or other shape
that is easily moved by blood flow.
The tubular bodies for the above embodiments have been described as
crimped braided tubes, however, the tubes can be made using other
manufacturing methods such as weaving, knitting, extruding, or
electro-spinning. Structures can also be manufactured with
alternating diameters or cross-sections, such as flat to round. In
addition, the tube can be made from a rolled sheet or other
material formed into desired tubular or substantially cylindrical
structures. Structural flexibility can then be adjusted either by
crimping or selective laser cutting, for example. If desired, the
tubular body can also be flattened to create a thin walled tape or
heat pressed to create oval sections.
Also, although crimping, or the use of axial/longitudinal
compression and heat is described to produce crimps or peaks and
valleys, other manufacturing methods of constructing peaks and
valleys can be utilized to achieve similar effects. For example, a
wire may be wound tightly around a braid placed on a mandrel. The
gaps between windings will create peaks and when the assembly is
heat set (with or without longitudinal compression) and the wire
removed, valleys will be formed where the wire compressed the braid
and peaks where the braid was exposed.
FIGS. 16A through 16C and FIG. 17 illustrate a portion of
micrograft 10 tubular body 12 constructed of 20 denier/18 filament
polyester yarn. FIG. 16A shows examples of an uncrimped tubular
body 171 alongside a crimped micrograft 10 tubular body 12 to
illustrate the formed macro peaks and valleys. FIG. 16B shows a
crimped tubular body alongside a tubular body that has been shape
set into a helical coil 172 post crimping similar to FIG. 3A. FIG.
16C shows micrograft 10 that has fluid 174 which has been drawn
into the micrograft via capillary action described earlier. FIG. 17
shows a tubular body with a marker band (stop collar) 22 attached
to the body as in FIG. 1.
Turning now the delivery of the micrografts, several embodiments of
delivery systems of the present invention are disclosed. Many of
the delivery systems enable over the wire insertion which minimizes
micrograft snaking inside the catheter as well as enables delivery
of longer length micrografts. The delivery systems also enable
retrievability of the micrograft after partial deployment, and in
some embodiments, even after full deployment.
Turning to a first embodiment and with reference to FIGS. 5A-5D, an
intra-aneurysmal micrograft delivery system is illustrated and
designated generally by reference number 54. The delivery system is
described below for delivering micrograft 10 but it should be
understood that it (as well as the other delivery systems described
herein) can be used to deliver any of the micrografts disclosed
herein. Delivery system 54 includes a pre-loaded delivery wire 62
for carrying the micrograft and a pusher catheter 58, the
pre-loaded delivery wire 62 positioned within the pusher catheter
58. Optionally the system could include a loading sheath similar to
the loading sheath of FIG. 7 described below which is positioned
thereover to retain the micrograft on the delivery wire 62. The
individual components of the delivery system can be removed from
the packaging during the procedure and assembled by inserting the
delivery wire 62 proximally through the catheter 58 creating a
junction 57 at the proximal end of the micrograft 10 and the distal
end of the pusher catheter 58. Alternatively, they can be
pre-packaged with the delivery wire 62 already positioned within
the pusher catheter 58 and a protective loading sheath similar to
the loading sheath of FIG. 7 positioned thereover to retain the
micrograft 10 on the delivery wire 62. This delivery system may be
used as a standalone delivery system to access the target anatomy,
or with a microcatheter as described below. Any necessary flushing
or coating activation can be done per physician's discretion prior
to insertion into the patient.
Delivery wire 62 has micrograft 10 mounted thereon at region 56.
Delivery wire 62 has a body with a length extending from proximal
end 64 to distal end 66 can range between about 20 cm and about 400
cm, and more particularly between about 100 cm and about 300 cm,
and even more particularly about 200 cm. Suitable diameters for the
delivery wire 62 can range from about 0.0025 inches to about 0.040
inches, and more narrowly between about 0.002 inches and about
0.035 inches. The overall diameter of the delivery wire may be
continuous, for example about 0.014'' or the wire may taper from
proximal to distal direction, for example about 0.007 inches to
about 0.003 inches. Other sizes are also contemplated, dependent on
the pusher catheter and/or microcatheter ID used for the
procedure.
The distal portion 68 of the delivery wire 62 can include a coil
and the very distal tip 66 of delivery wire 62 can be bulbous, of
increased diameter, or fitted with a marker band or coil. The
distal portion 68 of the delivery wire may be radiopaque as well as
able to be shape set to aid in tracking, vessel selection, and
intra-aneurysm maneuvering. For example the distal portion can be
shape set to J-shape as in FIG. 11A described below. The delivery
wire 62 may also be coated with a hydrophilic coating. The delivery
wire 62 includes a retaining structure such as a tapered region to
aid in retention of the micrograft 10 thereon. In alternative
embodiments, to further aid retention, or if a delivery wire is
utilized which does not have such retention structure such as a
standard guidewire, then a protective loading sheath can be
utilized. In another embodiment, the micrograft can be mounted
using the micrograft introducer system 136 as described below with
regard to FIG. 9.
Delivery wire 62 has a tapered region 70 (FIG. 5C) forming an
engagement structure for mounting the micrograft 10. A proximal
stop collar 22 is positioned over the tapered region 70. The stop
collar 22 can be attached to the delivery wire 62 or alternatively
and preferably form a retaining feature attached to an internal
portion of the micrograft 10. In either case, the proximal end of
the micrograft 10 is frictionally engaged and retained by the
delivery wire 62. Micrograft 10 is mounted coaxially (and slidably)
on wire 62 a distance L from the wire distal tip 66. The distance L
is set by the proximal stop collar 22 which interacts with wire
taper 70 as shown in FIG. 5C, or other hard stop on the wire (e.g.,
a marker band), and the overall length of the micrograft. For
instance, longer micrografts may have a small distance L. In some
embodiments, distance L may be zero and the hard stop may be on,
inside or near the distal end of the micrograft 10 to interact with
a bump, bulb or head (such has a head 184 of FIG. 5E described
below) on the distal end of the delivery wire 62 to prevent the
delivery wire 62 from passing through the distal end of the graft.
In this instance, the distal tip of the micrograft 10 would be
adjacent the distal end of the delivery wire 62 as in the
embodiment of FIG. 5E.
FIG. 5C shows an enlarged cross sectional view of the proximal end
of micrograft 10 with stop collar 22 engaging tapered region 70 of
the delivery wire 62. The stop collar 22 as shown is in the form of
a marker band to provide radiopacity for visualization. The wire
taper 70 acts as a proximal stop to prohibit proximal movement of
the micrograft 10 over the wire 62.
Other ways to couple or mate the micrograft and the delivery wire
62 are also contemplated. As mentioned earlier, proximal and distal
Nitinol parts may be added to the micrograft as stops, or other
parts and/or features (e.g., platinum marker band, notch, bump,
etc.) can be added to the delivery wire to act as stops. In some
instances, there may be no stop collar, the stop may be on the
distal end of the braid (as mentioned above), the pusher catheter
may act as the proximal stop, or the micrograft 10 can be sized to
be free to slide across the entire length of the delivery wire,
proximal to distal.
The pre-loaded delivery wire 62 may be supplied with one or more
micrografts covered by a protective cover such as cover 92 of FIG.
7. This cover 92 has a tapered tip tapering to a smaller outer
dimension for introduction into the lumen of a microcatheter or
component thereof.
In some embodiments, more than one micrograft can be loaded on the
delivery wire. They can be linked together on the delivery wire for
delivery using one of the frayed, Velcro-like ends 38 described
above with respect to FIG. 3 or inter-connected with assistance of
the coaxial delivery wire running through them. That is, the device
can in some embodiments be supplied pre-packaged with a plurality
of micrografts in line along the delivery wire.
As mentioned above, the delivery system 54 includes a pusher
catheter 58 having a lumen through which the delivery wire 62
extends. Pusher catheter 58 includes a catheter body 72 and a Luer
lock 74. Catheter body 72 is preferably of a variable stiffness
construction with a stiff proximal section, softer mid-section and
still softer distal section. Individual sections of the catheter
may be made up of polymer tubing with varying durometers to control
stiffness, proximal to distal. The body may also be made from a
variable stiffness, laser cut tube made of stainless steel alloy or
Nitinol, for example. If polymer tubes are used, the catheter may
also be a braid or a coil reinforced to keep from ovalizing. A
lubricous liner made from materials such as PTFE, ePTFE, or FEP may
also be added to the structure.
The outer diameter of the pusher catheter 58 is dimensioned to
slide freely inside microcatheters with inner diameters ranging
from about 0.008 inches to about 0.070 inches. Catheter body 72 can
include a hydrophilic coating on its outer diameter for lubricity.
The length of the catheter body 72 is preferably slightly shorter
than the delivery wire 62 to allow proximal access to the delivery
wire 62, i.e., holding the wire 62, while a micrograft (or multiple
micrografts) is loaded on the distal end. The inner diameter of
pusher catheter body 72 or the distal end is sized and shaped so
that the micrograft 10 cannot be forced inside the catheter body 72
during distal advancement or proximal pulling of delivery wire 62.
When loaded in the pusher catheter 58, the delivery wire 62 is
preferably free to rotate and to move in a linear (back and forth)
motion relative to the pusher catheter 58. Additionally, the pusher
catheter 58 can be designed to accommodate delivery of stents or
other devices or fluids to the target anatomy. In some embodiments,
a clearance between an outer dimension of the delivery member and
an inner dimension of the occluding device is substantially
fluid-tight before delivery into the aneurysm but sufficient to
enable slidable movement of the delivery member with respect to the
occluding device.
At or near the distal end of pusher catheter body 72 is radiopaque
marker band 76 which can be made of platinum/iridium and attached
with adhesive, heat shrink tubing, a swaging process, or other
known methods. Alternatively, the marker band can be placed inside
the pusher catheter 58 with the delivery wire 62 passing through
it. Other suitable radiopaque materials for marker band 76 include
gold, silver, and radiopaque shrink tubes, or metal coils for
example. A luer lock 74 can be positioned at the proximal end of
the catheter 58 and attached to the luer lock 74 is a rotating
hemostatic valve (RHV) 78 for saline, drug, contrast media or other
fluid introduction though the inner diameter of pusher catheter 58.
The RHV 78 also serves as a lock to stop relative movement between
the pusher catheter 58 and the pre-loaded delivery wire 62 when the
RHV 78 is tightened over (clamped onto) the wire. In some
embodiments, the pusher catheter 58 can be delivered pre-packaged
and sterile with an RHV as an accessory. In embodiments where a
co-axial catheter stent delivery system is used, a pusher catheter
may not be required as after stent deployment by the stent delivery
catheter, the micrograft loaded delivery wire can be inserted into
the stent delivery catheter to deploy micrografts.
As described earlier, the delivery wire 62 may be used as the
primary access wire as in conventional guidewires. FIG. 6
illustrates an alternate design to the over-the wire pusher
catheter, which is a rapid exchange pusher catheter designated
generally by the reference number 80. The rapid exchange (RX)
pusher catheter 80 has a catheter body 82 with marker band 76 at a
distal end and a stiff push wire 84. Catheter body 82 will share
many of the same features as the mid and distal section of catheter
body 72 described above, including coating. The stiff pusher wire
84, which may taper, can be made of stainless steel alloy, Nitinol,
or other suitable material. The pusher wire 84 may alternately be a
hypo-tube, with or without laser cutting, or a wire featuring a
non-round cross-section. The device may be supplied pre-packaged
and sterile. In use, the RX catheter may be inserted over the
delivery wire or guide wire before or after the aneurysm is
accessed by the wire.
FIG. 5E-5G illustrate a delivery system 180 for delivering the
micrograft 10' of FIG. 4A. The delivery system has a pusher member
186 and delivery wire 182 with an enlarged head 184. In the initial
position of FIG. 5E the tab 29a of micrograft 10' is bent
downwardly and the delivery wire 182 passes through window 29b. The
delivery wire 182 extends within micrograft 10' to the distal end
of the micrograft 10'. In this position, head 184 engages the
proximal edge of stop 22, e.g., distal marker band 22, on
micrograft 10'.
The pusher member or catheter 186 has an internal stop 188 at its
distal end to aid with pushing micrograft 10' as well as to inhibit
movement of micrograft 10' into the pusher member's inner diameter.
The pusher catheter 186 is shown by way of example without a luer
attachment. Both the pusher catheter 186 and the delivery wire 182
may be constructed as previously described. In addition, although
not shown, system 180 can include a protective introducer sheath
similar to the loading sheath 92 of FIG. 7 to limit micrograft
movement as well as to assist in micrograft introduction into a
microcatheter.
In the initial position, tab 29a of micrograft 10' is bent
downwardly and the delivery wire 182 passes through window 29b
(FIG. 5E). The delivery wire 182, as mentioned above, extends
inside the graft 10' such that enlarged head 184 comes into contact
with the proximal edge of stop 22. Note, although the stop 22 is
shown as open, it may be completely closed. Also, the stop may be
excluded and the braid may be melted to narrow or close the distal
end of the braid to prohibit the wire 182 from exiting. The use of
a distal stop also serves the purpose of keeping the micrograft 10'
in tension which aids in delivery by stretching and reducing the
outer diameter of the micrograft 10'.
The tab 29a provides a force against the delivery wire 182 to
retain the micrograft 10' on the wire 182. Upon delivery, the wire
182 is retracted to the position of FIG. 5F where delivery wire
enlarged tip 184 engages the tab 29a. Up to this position the
micrograft 10' can be retrieved from the aneurysm and/or maneuvered
therein. Next, pusher catheter 186 is advanced (or wire tip
retracted) to force the tab 29a to the position of FIG. 5G,
therefore enabling full retraction of the enlarged head 184 of the
delivery wire 182 through window 29b for release of the micrograft
10' from the delivery wire 182. FIG. 5H shows the tab 29a returned
to its original position longitudinally aligned with the micrograft
10' after retraction of the delivery system.
FIG. 7 illustrates another embodiment of an intra-aneurysmal
micrograft delivery system generally referred to by reference
number 86. Delivery system 86 comprises a pusher wire 88 and a
loading tube 92. Pusher wire 88 includes an elongate tapering
flexible wire that can be made from stainless steel, or
alternatively, Nitinol, plastic or other inert or biocompatible
material or combination thereof. Although shown as a wire, the
pusher wire can alternatively be a hypo-tube with a Luer lock.
At the distal end of pusher wire 88 are expanding grasper members
or arms 94, 98. Although there are four grasper arms in this
design, more or less than four arms may be used. The arms 94, 98
can be made of shape set shape memory material such as Nitinol,
spring tempered stainless steel, radiopaque metal, or other
suitable material. The arms 94, 98 can alternatively be
manufactured from a metal or elastic tube which is laser cut to
create deflectable arms. Attached to the distal end of one or more
of the grasper arms are radiopaque bands (see labeled bands 102,
106, and 108; the fourth band not shown since the fourth arm is not
shown). The bands can be attached with glue, solder or other
methods. The proximal ends of the arms are attached to the pusher
wire 88 by a coil 110 which can be made of wound stainless steel or
platinum iridium, for example. Attachment methods may include
gluing, welding, or soldering. The use of the grasping arms has the
advantage of enabling grasping of the micrograft after full
deployment to retrieve/remove the micrograft or to
maneuver/reposition the micrograft within the aneurysm as described
below.
The pusher wire 88 has a length (including arms) between about 20
cm and about 400 cm, more narrowly between about 100 cm and about
300 cm, for example about 200 cm. Suitable diameters for the pusher
wire 88 can range from about 0.006 inches to about 0.040 inches,
more narrowly between about 0.008 inches and about 0.035 inches.
The overall diameter of the pusher wire 88 may taper from proximal
to distal, for example about 0.014 inches tapering to about 0.003
inches. The pusher wire 88, either in part or whole, may be coated
with a hydrophilic or PTFE coating for lubricity
Loading tube 92 is made of either metal or plastic and preferably
has distal taper 112 for mating with a microcatheter Luer taper.
The loading tube 92 preferably has a length sufficient to cover the
entire micrograft 90 and at least a portion of coil 110. The inner
diameter of the loading tube 92 is preferably close to the inner
diameter of the microcatheter to which it will mate. A range for
the inner diameter may be between about 0.008 inches and about
0.070 inches. The loading tube may have a crimp or other fixation
method to prevent relative movement to the pusher wire 88. If used
on a structure having a Luer or other attachment on its proximal
end, the introducer may have a lengthwise slit to aid in removal
(i.e., peel-away).
One way to load micrograft 90, which has proximal band 114, e.g., a
marker band, is to position the loading tube 92 on pusher wire 88
just proximal to the two pair of grasper arms 94, 98 so that the
arms are in their normal expanded position. The band 114 on
micrograft 90 is then positioned between bands 102 and 104 (one on
each arm of arms 94) and bands 106 and 108 of arms 98. Note to
achieve axially spaced bands, the arms 94 can be shorter than arms
98 so the bands 102, 104 are proximal of bands 106, 108, or
alternatively, the arms 94, 98 can be the same size and bands 102,
104 can be placed on a more proximal position of arms 94 (spaced
from the distal end) while bands 106, 108 can be placed on a distal
end or more distal position of arms 98. The loading tube 92 is then
advanced forward (distally) compressing the pusher arms 94, 98 to a
collapsed or compressed position to engage (grasp) the band 114 to
retain the micrograft 90 in place. Thus, band 114 forms an engaging
or retention structure for engagement by the pusher (delivery) wire
88 to retain the micrograft 90 on the wire 88.
Note micrograft 90 is similar to micrograft 10 except for the
proximal band 114 which is positioned around a portion of the
braided structure.
Note alternatively, instead of the micrograft having a single
proximal marker band, it may have two proximal bands where the
bands of the pusher wire sit to create a lock when compressed
inside the lumen of the loading tube. Alternatively, a micrograft
with an internal coil may have proximal coil windings spaced to
have a gap that allows radial compression and grasping by the bands
of the pusher wire.
FIG. 8 illustrates yet another embodiment of an intra-aneurysmal
micrograft delivery system generally referred to by reference
number 116. Delivery system 116 is a neurovascular stent-graft kit
that comprises a pusher wire 118 with distal band 120, stent or
flow diverter 122 with proximal arms with bands 124 and 126 and
distal arms with bands 128 and 130, micrograft 132 with proximal
band 134, and loading tube 133. The micrograft 132 is locked
proximally by the stent 122 and stent bands 128 and 130 and loading
tube 133. Stent or flow diverter 122 is in turn locked to pusher
wire 118 using a similar locking concept as bands 124, 126 are
blocked by band 120. The number of arms for both locking systems
may vary to be more or less than two. Delivery system 116 can also
be configured to have a through lumen for guidewire delivery.
The delivery system 116 provides a single delivery system that can
deliver a micrograft and a stent that can be combined on site to
form a neurovascular stent-graft. Alternately, the stent may be
permanently attached to the pusher wire and acts as a temporary
stent to push grafts into the aneurysm.
FIG. 9 illustrates a micrograft introducer system 136 which may be
used to mount micrografts on a delivery wire or on a guidewire
before or during a medical procedure. Micrograft loader introducer
system 136 comprises introducer sheath 138 loaded with micrograft
10. The introducer sheath includes tubular body 140, Luer lock 142,
and stop tube 144. Tubular body 140 can be made of metal, plastic
or a combination of materials and sized with an inner diameter
between about 0.008 inches and about 0.070 inches and a length that
covers all or substantially all of the micrograft 10. The distal
tip of the tubular body 140 may be straight or tapered to help in
micrograft introduction and handling. The Luer lock can be attached
to an RHV such as RHV 78 of FIG. 5D for the introduction of fluid
such as, saline or contrast media, guide or delivery wires and
pusher catheters. The stop tube 144, which is optional, has a
through lumen and can be made of plastic or metal and may have a
taper proximal to distal. The purpose of the stop tube is to
prohibit the micrograft from exiting the tubular body 140 prior to
loading and may be removed prior to insertion.
Although FIG. 9 shows only one micrograft, multiple micrografts may
be delivered in a single introducer sheath. They may be free to
move relative to one another or linked together using the frayed
ends method, for example, as described above. Micrografts having
secondary shapes will generally be linear or straight when loaded
into the introducer sheath such that they are concentric.
Introducer system 136 is delivered pre-packaged and sterilized.
Once opened, an RHV and syringe may be attached to the Luer to
introduce fluids. A delivery wire or guidewire may be pushed into
the introducer sheath 138 to mount the micrograft(s) on the wire or
alternatively the introducer sheath 138 may be mated with the
proximal end of the microcatheter and the micrografts may be pushed
proximally through the sheath 138 and into the microcatheter using
a pusher catheter, with or without a wire, or with a commercially
available pusher wire.
The micrografts disclosed herein can be preset to a non-linear
configuration and advanced to the aneurysm in a substantially
linear configuration and then return to the same non-linear
configuration or different non-linear configuration when delivered
into the aneurysm, depending on the space within the aneurysm.
FIGS. 10 through 11F show the preferred method of using
intra-aneurysmal micrograft delivery system 54 of FIG. 5A to deploy
micrograft 10 of FIG. 1. (Other micrografts described herein can be
inserted in a similar fashion). The micrograft delivery method, as
well as the "viscosity lock" function (described below) are
depicted in flow chart form in FIGS. 18 and 19. Before
implantation, the delivery system may be prepared prior to patient
insertion as described above or as preferred by the physician.
Typical intracranial aneurysm access requires inserting a guide
catheter into the femoral artery and then tracking a microcatheter
in combination with a primary guidewire through the vasculature
until the aneurysm site is reached. Once there, the primary
guidewire is removed and replaced with an embolization system. FIG.
10 shows micrograft delivery system 54 of FIG. 5A being inserted as
a unit into the proximal end of microcatheter 146 (with attached
RHV 148), the microcatheter 146 having been inserted through the
guide catheter and advanced to the aneurysm site and the primary
guidewire removed.
FIG. 11A illustrates the distal tip 66 of delivery wire 62 exiting
microcatheter 146 that has been positioned inside aneurysm 150 and
is held in place using a "jailing" stenting technique, surrounded
by blood 152. Jailing refers to the use of a stent or flow diverter
154 to pin the distal tip of the microcatheter between the parent
vessel intima and the stent or flow diverter 154, so that the
microcatheter tip is held within the aneurysm and delivered
occluding devices, e.g., micrografts 10, are kept out of the parent
vessel lumen. Other techniques that may be used instead of jailing
include temporary stenting and balloon remodeling. It is also
contemplated that the micrografts of the present invention be
deployed without the use of such parent vessel support (stent or
flow diverter) devices.
Once the system is in place as shown in FIG. 11A, the exposed
delivery wire tip 66, which has the pre-bent curve as shown, is
slowly retracted into the micrograft 10. The retraction can be done
in incremental steps of a few centimeters or completely until it
reaches a location at, or near, the pusher/micrograft juncture 57
(see FIG. 5A). As the delivery wire 62 is retracted proximally
toward junction 57, blood 152 will be drawn into the micrograft's
inner lumen to fill the volume previously occupied by the delivery
wire 62, as depicted in FIGS. 11B and 11C. This filling action
occurs through a combination of the unique internal capillary
features of the micrograft described earlier and due to a
syringe-like "piston" effect of the receding wire.
With the delivery wire 62 pulled back and in some embodiments
pulled back to a locked position against tab 21a, as in the
embodiment of FIG. 5F, the micrograft 10 can be pushed forward off
the wire 62 and into the aneurysm as illustrated in FIG. 11D using
the pusher catheter 58 (FIG. 5A) as it is advanced distally and
engages the proximal end of the micrograft 10. Note that if the
delivery system does not feature a mechanical lock physically
connecting the pusher catheter 58 or delivery wire 62 to the
micrograft 10, the micrograft 10 may still be retrieved due to a
"viscosity lock" (described below) that is formed inside the
microcatheter 146, between the delivery system components and
micrograft, once surrounded by a viscous liquid (e.g., blood). This
lock allows the micrograft 10 to be advanced and retracted while
the proximal end of the micrograft 10 remains inside the lumen of
the microcatheter 146 until desired placement is achieved.
Micrograft 10 is pushed forward by pusher catheter 58 and the wire
62 can be pulled further proximally to junction 57, if it is not
positioned there already. Once the wire 62 reaches junction 57, the
inner lumen of the micrograft 10 will be completely filled with
blood 152 that displaces the wire 62 and with any liquid that has
been present (e.g., contrast). Since blood now fills the inside
lumen of the micrograft 10 and has already permeated the braided
walls via the aforedescribed capillary action, the saturated device
is composed in part of the patient's blood. Thrombosis and cell
in-growth through the microporous yarns will be accelerated as the
blood becomes trapped and stagnant within the micrograft (implant)
after delivery.
Note that blood can enter the lumen of the micrograft 10 through a
distal opening of the lumen and/or through other intermediate or
proximal regions of the lumen spaced from the distal end as blood
is absorbed through the braided structure. As blood enters such
intermediate or proximal regions, it spreads in various dimensions
as well as is directed proximally due to the aforedescribed
capillary action.
As the micrograft 10 is deployed into the aneurysm, it will take on
any preset secondary shapes and random shapes due to contact with
aneurysm walls or the stent/flow diverter 154, as shown in FIGS.
11D and 11E. That is, in these Figures, micrograft 10 has a pre-set
U-shape as shown, however, this shape can change as it contacts the
aneurysm wall and/or stent 154. If the proximal end of micrograft
10 remains inside the microcatheter, the micrograft 10 can be
retracted and repositioned at any time prior to full deployment as
described above. The micrograft 10 will be fully deployed and
disengage from the delivery system once the distal tip of the
pusher catheter 58 reaches or exits the distal end of the
microcatheter 146. FIG. 11E shows an enlarged cross section of the
fully deployed pre-shaped blood filled micrograft 10 of FIG.
11D.
After the first micrograft 10 has been deployed, the delivery wire
62 and pusher catheter 58 are removed and, if needed, another
micrograft 10 is loaded on the wire 62 or a new delivery system is
opened, and the deployment process is repeated as described above.
Multiple micrografts can be deployed by repeating the above steps
until the aneurysm is sufficiently packed (per physician
discretion) as shown in FIG. 11F. If needed, the microcatheter tip
or the delivery wire 62 can be used in between packing or during
packing to move or compress micrografts within the aneurysm. Once
the aneurysm is sufficiently packed, the microcatheter is removed
and the stent or flow diverter 154 continues to expand to cover the
neck of the aneurysm 158 to thereby block exit of the micrografts
10 from the aneurysm sac. Together, micrograft 10 and stent or flow
diverter 154 form neurovascular stent-graft 160, as shown in FIG.
11F.
As mentioned above, delivery system 54 features a temporary liquid
seal or "viscosity lock" effect inside the microcatheter which
allows limited retrieveability (push/pull) of the micrograft during
placement. The "pull" of the lock is generated by the tip of the
pusher catheter 58, which creates a syringe-like "piston" within
the fluid-filled microcatheter 146. Functionality of this lock is
dependent on clearances between the microcatheter lumen, proximal
micrograft 10 body, adjacent pusher 58 tip, the delivery wire 62,
as well as the viscous and cohesive properties of the fluid
medium.
The flow chart of FIG. 19 describes the steps of the viscosity lock
function which are as follows: 1) Inside the aneurysm, align tip of
delivery wire 62 with distal end of micrograft 10. 2) Retract wire
62 to draw blood inside micrograft lumen up to the pusher junction
57. 3) Push delivery system (pusher 58+wire 62) to advance
micrograft 10 out of catheter 146. 4) While maintaining proximal
end of micrograft 10 inside catheter 146, pull on delivery system
to retract micrograft 10. 5) Re-deploy micrograft 10 once
re-positioned by pushing on delivery system. 6) Release blood
filled micrograft 10 by pushing proximal end of micrograft 10 out
of catheter 146. 7) Repeat process to deliver another micrograft
10, or remove delivery system and load additional micrograft 10
onto distal wire tip.
In order for the viscosity lock to work, viscous liquid (i.e.,
blood) must fill the microcatheter past the micrograft/pusher
junction. Once viscous fluid fills the micrograft(s) 10 and gaps
around the pusher junction 57, it acts as a "gasket", or a seal,
around the pusher/micrograft junction 57 during any displacement
(i.e., as the pusher is retracted). The action of pulling the
pusher 58 (i.e., the piston) adjacent to the proximal end of the
micrograft now creates a low pressure volume. This causes the
micrograft(s) 10 suspended in blood to get suctioned and retract
within the microcatheter 146.
The micrograft 10 may also be retractable if the delivery wire
distal tip 66 is pulled back proximal to the distal tip of pusher
58 or removed completely. High friction or pull resistance are more
likely to break the "viscous lock", so the preferred application
for this retrieval method is with shorter, lower friction devices
or where minimal tortuosity and resistive forces are involved.
In some embodiments of the micrograft delivery system, a pusher
wire or delivery wire may not be present inside the micrograft
lumen and internal filling of the micrograft with blood will be
induced by pressure from the patient's circulatory system or via
capillary forces. Capillarity can be achieved by the micrograft
having appropriately sized inner diameter or pores, as described
earlier. Hence, the absorption of blood into micrograft depicted in
FIG. 11C can occur upon contact with blood even if delivery wire or
external force is not used to draw blood in.
FIGS. 12A through 12C show directed delivery of micrograft 10 of
FIG. 1 inside an intracranial aneurysm. Other micrografts described
herein can be delivered in a similar manner. Unlike micrograft
delivery described in FIGS. 10 and 11A-11F above, in the embodiment
of FIGS. 12A and 12B, the shaped delivery wire 62' remains in the
aneurysm so that the micrograft deployment can be directed to a
targeted location (neck) within the aneurysm sac. FIG. 12A
illustrates a distal tip 66' of delivery wire 62' that has been
shape set in a "J" and deployed so that the "J" points at the stent
or flow diverter 154 covering the neck of the aneurysm. As the
pusher catheter 58 is advanced distally, the micrograft 10 will
deploy and follow along the delivery wire 62' in a direction
denoted by arrow 162 towards the stent or flow diverter 154.
FIG. 12B illustrates a delivery wire 62' that has been shape set
with a "J" and advanced into the dome of the aneurysm. As the
micrograft 10 is advanced it will follow the curvature of the wire
62' in a direction denoted by arrow 164.
FIG. 12C illustrates that the microcatheter 146 can be used to
direct micrograft deployment within the aneurysm. The delivery wire
has been pulled back into microcatheter 146 which is seated in the
neck of the aneurysm 158. As the micrograft 10 is advanced it will
follow the direction denoted by arrow 166. The tip of the
microcatheter 146 can be curved to direct the micrograft 10. When
the micrograft 10 encounters barriers, such as the aneurysm wall,
it will easily change direction as depicted.
FIG. 13 illustrates the deployment of flow directed micrografts 168
using intra-aneurysmal micrograft delivery system 54 with delivery
wire 62' having a "J" form at its tip and extending from
microcatheter 146. Micrografts 168 can have the same structure as
other micrografts described herein. Flow directed micrograft 168
can be any length, but shorter lengths such as about 2 mm to about
5 mm are utilized in this embodiment so as to move with blood flow.
Since the flow directed micrografts 168 tend to be shorter than
micrografts configured to fill the aneurysm, many more flow
directed micrografts can be loaded onto the delivery wire and
consecutively deployed, as illustrated in FIG. 13. Micrograft 168
has been shape set into a "C" shape, however, other shapes are also
contemplated as discussed above.
As each micrograft 168 is advanced distally off the delivery wire
62', it will be caught up in blood flow exiting the neck of the
aneurysm. Due to the stent or flow diverter 154 blocking the neck
158, micrograft 168 will be restricted from exiting into parent
vessel 170. When a sufficient amount of micrografts 168 are
introduced into the aneurysm, the micrografts will pile up and clog
or create a localized graft at the stent/flow diverter and neck
interface. Over time, thrombus will form above the clog to aid in
closing off the aneurysm. The smaller, shorter micrografts are
intended to provide a more complete obstruction or fill voids at
the aneurysm neck.
FIG. 14 illustrates microcatheter 146 positioned inside the parent
vessel 170. This embodiment differs from the previous embodiments
in that instead of extending in the space between the stent 154 and
parent vessel 170, the microcatheter 146 extends through the struts
or pores of stent or flow diverter 154. In all other respects, the
system is the same as that of the aforedescribed systems. Note
micrograft 10 is shown exiting the microcatheter 146 into the
aneurysm. Longer length or shorter length micrografts can be
delivered.
As discussed earlier, the delivery wire 62 can be a guidewire.
Therefore, if desired, the micrograft delivery system with
guidewire can be loaded into the microcatheter prior to catheter
placement. The entire assembly, microcatheter and micrograft
delivery system, can then be tracked to the aneurysm site using the
delivery system's guidewire as the primary tracking wire.
Alternately, the guidewire and microcatheter can be tracked to the
aneurysm site and rapid exchange catheter, e.g., pusher catheter 80
of FIG. 6, can be advanced subsequently.
FIG. 15 illustrates the distal end of intra-aneurysmal micrograft
delivery system 86 of FIG. 7 deploying micrograft 90. Micrograft 90
has been released from arms 94, 98 and has assumed a pre-biased
(pre-set) shape. As noted above, the micrografts can be pre-set to
a variety of configurations and the shapes illustrated in the
drawings are provided by way of example. If desired, the micrograft
90 can be retrieved by capturing a portion of the structure between
arms 94, 98, and advancing the microcatheter 146 over the arms to
compress the arms. Alternately, the delivery arms 94, 98 can be
used to compress or move the micrograft around the aneurysm to aid
in packing.
FIG. 18A provides a flow chart for one method of placing a
micrograft of the present invention. This method utilizes the
delivery system of FIGS. 5A and 5C. The steps include: 1) Insert
micrograft(s) over distal end of delivery wire 62 until micrograft
rests on stopper or wire taper 70. 2) Insert delivery wire 62 into
pusher catheter 58. 3) Insert delivery system into RHV 78 of
microcatheter. 4) Track delivery system until wire tip 66 reaches
aneurysm. 5) Pull back wire 66 and align with distal marker band of
micrograft in aneurysm. 6) Fill micrograft with blood by retracting
wire tip 66 into the micrograft. 7) Deploy micrograft by advancing
pusher 58. Retract device if proximal end still in microcatheter.
8) Remove delivery system from microcatheter. 9) If needed, repeat
steps to deploy additional micrografts.
FIG. 18B provides a flow chart for another method of placing a
micrograft of the present invention. This method utilizes the same
delivery system of FIGS. 5E-5H. The steps include: 1) Remove device
from packaging and prepare per Instructions for Use (IFU). 2)
Insert delivery system with micrograft into microcatheter RHV. 3)
If present, remove introducer sheath once micrograft is inside
microcatheter. 4) Track delivery system until wire tip 184 and
distal end of micrograft reach the treatment site. 5) Fill
micrograft with blood by incrementally retracting wire tip 184 just
distal of the micrograft lock (tab 29a). 6) Deploy micrograft by
advancing delivery system (pusher 186 and wire 182). Pull delivery
system to retract micrograft if necessary. 7) Once out of
microcatheter, detach micrograft by retracting wire 182 (or
advancing pusher) until wire bulb 184 pulls through micrograft lock
(tab 29a) and into the pusher 186. 8) Remove delivery system from
microcatheter. 9) If needed, repeat steps to deploy additional
micrografts.
Note the delivery systems and occluding devices (micrografts)
disclosed herein have been described for use for treating
intracranial aneurysms. It should be appreciated that the delivery
systems and occluding devices (micrografts) can also be utilized
for treating aneurysms in other regions of the body or for treating
other vasculature or for treating non-vascular diseases.
Note the delivery systems disclosed herein can be utilized to
deliver the various micrografts disclosed herein and specific
micrografts discussed in conjunction with specific delivery systems
are provided by way of example.
The above delivery systems and concepts are preferred ways to
deliver the intra-aneurysmal micrograft. The micrograft however may
alternatively be constructed to mate with other microcoil delivery
systems that provide a timed and controlled release, e.g.,
electrolytic detachment as described in U.S. Pat. No. 5,354,295 and
its parent, U.S. Pat. No. 5,122,136, both to Guglielmi et al.,
interlocking ball and key way as described in U.S. Pat. No.
5,261,916 to Engelson, and pusher with mating ball configuration as
described in U.S. Pat. No. 5,304,195 to Twyford et al.
In some applications, other vaso-occlusive devices such as platinum
microcoils may be used in combination with the micrografts of the
present invention to occlude the aneurysm.
While the above description contains many specifics, those
specifics should not be construed as limitations on the scope of
the disclosure, but merely as exemplifications of preferred
embodiments thereof. Those skilled in the art will envision many
other possible variations that are within the scope and spirit of
the disclosure as defined by the claims appended hereto.
* * * * *